ying tung chan and chi man yip · 11/23/2018  · ying tung chan and chi man yip abstract why are...

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S EARCH R ELATIVITY Ying Tung Chan and Chi Man Yip * Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem- ployment rate (AUR) uncorrelated with the distribution of educational level? Why is the unemploy- ment rate of the postgraduates about half the AUR? We propose a theory to answer these questions. Our theory suggests that a job-finding rate increases with the relative position of a search intensity dis- tribution (search relativity). We illustrate our theory via a search-theoretic model and derive a novel formula to disaggregate the AUR into the unemployment rates by educational level simply using one easily accessible sufficient statistic—the distribution of educational attainment in the labor force. In most states, the distributions of the predicted and the actual unemployment rates by educational level are found statistically identical, suggesting that search relativity is one of the key determinants of a job-finding rate and is the major source of heterogeneity in the unemployment rate. KEYWORDS: Distribution of Search Intensity, Matching Technology, Unemployment Distribu- tion. JEL Classification Numbers: C78, D3, E24, J64. * Chan: The Research Institute of Economics and Management, Southwestern University of Finance and Economics, Chengdu, China (email: [email protected]); Yip: Department of Economics, the University of Calgary, 2500 Univer- sity Dr. N.W., Calgary, AB, T2N 1N4 (email: [email protected]) We would like to thank Scott Taylor and Trevor Tombe for their patience, guidance, encouragement support, and our many insightful conversations. We thank David Card, Nicole Fortin, Junichi Fujimoto, Fabian Lange, Charles Ka Yui Leung, Lucija Muehlenbachs, Ron Siegel, Pascal St-Amour, Stefan Staubli, Atsuko Tanaka, Yikai Wang, Jean-Francois Wen, Alexander Whalley, Russell Wong, and seminar participants at the 2018 SOLE@MEA Conference, the 2018 WEAI Conference, the 2018 SEA Conference, the 2017 SOLE Annual Conference, the 2017 ASSA Annual Conference, the 2017 China Meeting of the Econometric Society, the 2016 Canadian Economics As- sociation Annual Conference, the City University of Hong Kong, and the University of Calgary for their useful comments. We owe our classmates Younes Ahmadi, Yutaro Sakai, Yan Song, Meng Sun, and Qian Sun for their suggestions.

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Page 1: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

SEARCH RELATIVITY

Ying Tung Chan and Chi Man Yip∗

Abstract

Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-

ployment rate (AUR) uncorrelated with the distribution of educational level? Why is the unemploy-

ment rate of the postgraduates about half the AUR? We propose a theory to answer these questions.

Our theory suggests that a job-finding rate increases with the relative position of a search intensity dis-

tribution (search relativity). We illustrate our theory via a search-theoretic model and derive a novel

formula to disaggregate the AUR into the unemployment rates by educational level simply using one

easily accessible sufficient statistic—the distribution of educational attainment in the labor force. In

most states, the distributions of the predicted and the actual unemployment rates by educational level

are found statistically identical, suggesting that search relativity is one of the key determinants of a

job-finding rate and is the major source of heterogeneity in the unemployment rate.

KEYWORDS: Distribution of Search Intensity, Matching Technology, Unemployment Distribu-

tion.

JEL Classification Numbers: C78, D3, E24, J64.

∗Chan: The Research Institute of Economics and Management, Southwestern University of Finance and Economics,Chengdu, China (email: [email protected]); Yip: Department of Economics, the University of Calgary, 2500 Univer-sity Dr. N.W., Calgary, AB, T2N 1N4 (email: [email protected]) We would like to thank Scott Taylor and Trevor Tombefor their patience, guidance, encouragement support, and our many insightful conversations. We thank David Card, NicoleFortin, Junichi Fujimoto, Fabian Lange, Charles Ka Yui Leung, Lucija Muehlenbachs, Ron Siegel, Pascal St-Amour, StefanStaubli, Atsuko Tanaka, Yikai Wang, Jean-Francois Wen, Alexander Whalley, Russell Wong, and seminar participants at the2018 SOLE@MEA Conference, the 2018 WEAI Conference, the 2018 SEA Conference, the 2017 SOLE Annual Conference,the 2017 ASSA Annual Conference, the 2017 China Meeting of the Econometric Society, the 2016 Canadian Economics As-sociation Annual Conference, the City University of Hong Kong, and the University of Calgary for their useful comments.We owe our classmates Younes Ahmadi, Yutaro Sakai, Yan Song, Meng Sun, and Qian Sun for their suggestions.

Page 2: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

1 Introduction

At least since Keynes (1936), economists have been studying the determinants of the average wage

rate and the aggregate unemployment rate (AUR). Over the past few decades, the distributions of

wages, income, wealth, consumption, health, mortality, etc. have attracted much attention from both

empirical and theoretical studies.1 And yet, perhaps surprisingly, works, especially theoretical ones,

on the unemployment distribution and its properties are sparse. This paper investigates why the

unemployment rate differs across demographic groups.

Human capital is one of the key determinants of many labor market variables, such as wages and

their distribution (Mincer, 1958; Ben-Porath, 1967; Griliches, 1977; Becker, 1994). While schooling

is one of the major channels to accumulate human capital, heterogeneity in labor market outcomes

by educational level is huge. Inspired by the human capital theory, this paper pays attention to the

heterogeneity in the educational unemployment rate—the unemployment rate by educational level.

However, the theory proposed by this paper can be applied to explain the heterogeneity in the unem-

ployment rate by any demographic group, not just by educational group.

1.1 Two Seemingly Unrelated Features of Unemployment

We begin with the documentation of two seemingly unrelated features of unemployment, namely the

statistical puzzle of unemployment and the magic number of “one-half”.

The Statistical Puzzle of Unemployment. Figure 1 shows that unemployment rates are lower at

higher educational levels in the United States. Each line represents the unemployment rate of each

educational level during 1994-2015. The higher the educational level, the lower is the unemploy-

ment rate. While these five lines are completely segregated, this negative relationship holds over 20

years. Indeed, the documentation of this relationship has a long history (Ashenfelter and Ham, 1979;

Mincer, 1991), and we extend the documentation period of this relationship to 2015.2

Statistically, the AUR is likely lower at a higher fraction of high-educated workers in any econ-

omy. The AUR is the weighted average of the unemployment rate of each educational category, with

the weight equal to the fraction of each category. While high-educated workers have a lower risk

of unemployment than their low-educated counterparts, the weighted average of the unemployment

rate, the AUR, is expected to decrease with the fraction of high-educated workers.

However, Figure 1 illustrates that the AUR and the fraction of the high-educated are uncorre-

lated during 1994-2015. Moreover, we show in the online Appendix A that these two variables are

1Readers who are interested in the empirical studies on wage distributions and its dynamics are referred to Juhn et al.(1993), DiNardo et al. (1996), Katz et al. (1999), Lemieux (2006), and Autor et al. (2008). Those who interested in thetheoretical works are referred to Galor and Zeira (1993), Burdett and Mortensen (1998), Krusell and Smith (1998), Postel-Vinay and Robin (2002), Shi (2009), Hornstein et al. (2011), Moscarini and Postel-Vinay (2013), Jones and Kim (2014), andGabaix et al. (2016).

2Also, Topel (1993) finds that men of lower wages have a higher risk of unemployment. While men with higher educa-tional levels receive a higher average wage, his finding coheres with our documentation.

1

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uncorrelated and their cyclical components are also uncorrelated in each year during 1994-2015. Ob-

viously, the increasing fraction of the high-educated must have adjusted the unemployment rates of

the high- and/or the low-educated to reconcile the two documentations in Figure 1. Interestingly, this

adjustment always ceases at the situation, in which the AUR and the fraction of the high-educated are

uncorrelated, and thus raises a statistical puzzle: what economic mechanism makes the AUR and the

fraction of the high-educated always uncorrelated?

Figure 1: The Statistical Puzzle of Unemployment

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High-School DropoutsHigh-School GraduatesAssociate's Degree HoldersBachelor's Degree HoldersPostgraduates

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20 25 30 35 40 45Proportion of High-Educated Workers

Notes: The left figure displays the educational unemployment rate. The right figure displays the correlation between theaggregate unemployment rate and the fraction of high-educated workers in the United States. The high-educated are definedas those who are bachelor’s degree holders and the postgraduates. Each dot illustrates the average aggregate unemploymentrate and the average fraction of high-educated in each state during 1994-2015. DC is excluded because it is an outlier. In thesefigures, data are collected from the Current Population Survey 1994-2015. Samples are restricted to labor force participantsaged 25-60. Samples below 25 years old are excluded because Ph.D holders are likely graduated and enter the labor marketafter 25.

The Magic Number of “One-Half”. Figure 2 displays the correlation between the unemploy-

ment rate of the postgraduates and the AUR in the United States.3 The dash line is the fitted value, and

the solid line represents the mathematical relation in which the unemployment rate of the postgrad-

uates is half the AUR. Clearly, the two lines are close to each other, and the observations lie around

these two lines, suggesting that the unemployment rate of the postgraduates is about half the AUR.

Why is the unemployment rate of the postgraduates about half the AUR? Can it be other numbers? If

not, what economic mechanism creates the number of “one-half”?

The purpose of this paper is twofold: to explain that the heterogeneity in the unemployment rate

emerges mainly via a subtle relation between a job-finding rate and the distribution of search inten-

sity, and to show that the two seemingly unrelated features of unemployment is mainly attributable

to this subtle relation. Despite a voluminous literature on the AUR (Ljungqvist and Sargent, 2008;

3This feature can also be found in Canada and the United Kingdom using the Canadian Labor Force Survey and theUnited Kingdom Labor Force Survey, respectively.

2

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Figure 2: The Correlation between the Aggregate Unemployment Rate and the Unemployment Rate ofthe Postgraduates, 1994-2015

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2 3 4 5 6 7Aggregate Unemployment Rate (in %)

Slope: 0.44

Notes: This figure displays the relationship between the aggregate unemployment rate and the unemployment rate of post-graduates. The horizontal axis is the average aggregate unemployment rate of the corresponding state during 1994-2015. Thevertical axis is the average unemployment rate of the postgraduates in the corresponding state during 1994-2015. The dot lineis the fitted value, in which the slope is 0.44. The solid line represents the unemployment rate of the postgraduates is half theaggregate unemployment rate. Data are collected from the Current Population Survey 1994-2015. Samples are restricted tolabor force participants aged 25-60.

Elsby et al., 2009; Davis et al., 2010; Shimer, 2012; Sahin et al., 2014), discussions on unemployment

distributions are rare because the features of an unemployment distribution seem unrelated to each

other. If the properties of the unemployment rate by educational attainment are mastered well, the

properties of the AUR will be well understood, not vice versa. Therefore, to study the two seemingly

unrelated features of unemployment not only opens the “black box” of the unemployment distribu-

tion, but it also complements the literature on the AUR, enhances our understanding of the functioning

of the labor market, and provides insights how labor market policies could affect the unemployment

distribution.

1.2 Search Relativity Theory and Related Literature

Ask anyone about the relationship between a search intensity level and a job-finding rate, and what

first comes to his or her mind is likely that a job-finding rate increases with a search intensity level.

Despite no economy-wide experiment, we may observe that those who search more intensively tend

to get rid of unemployment faster. This may formulate our belief that a higher level of one’s search

intensity increases his or her job-finding rate.

This paper argues that a matching function maps one’s percentile rank in a search intensity dis-

tribution into his or her job-finding rate. Hence, the heterogeneity in job-finding rates arises from

the relative position in an intensity distribution (hereafter, we call it search relativity when appropri-

3

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ate). This paper shows that this search relativity accounts in large part for the heterogeneity in the

unemployment rate.

This paper demonstrates our search relativity theory using a search-theoretic model with hetero-

geneous workers. The key innovation of our theory is that an unemployed worker chooses his own

search intensity level to maximize his value function, and his job-finding rate increases with his rela-

tive position in an intensity distribution. In pursuit of a higher job-finding rate, unemployed workers

are required to have a slightly better curriculum vitae, perform slightly better in a job interview, and

devote slightly more time to seek jobs than the candidates ranked slightly higher in the intensity lad-

der. To increase one’s search intensity without climbing up an intensity ladder does not enhance his

job-finding rate. Hence, the determination of the optimal search intensity is challenging because it re-

quires unemployed workers to consider both a marginal search cost and whether an additional search

effort allows them to climb up an intensity ladder. We introduce the notion of the Nash equilibrium to

solve this problem. One of the striking results is that the distributions of search intensity and human

capital in unemployment are identical in the Nash equilibrium.

According to our theory, increasing ones’ search intensity level increases their relative positions

in an intensity ladder and thus their job-finding rates: their unemployment rates decline. Meanwhile,

it creates a negative externality on others: there exist workers whose rank declines. Consequently, the

rise in their search intensity levels has no effect on the AUR; a higher fraction of workers who search

intensively has no effect on the AUR. Analogously, because unemployed workers with a higher edu-

cational level tend to search more intensively, their higher percentile rank in the intensity distribution

returns them higher job-finding rates via a matching function. Consequently, their unemployment

rates are lower, and a higher fraction of high-educated workers and the AUR are independent, ex-

plaining the statistical puzzle of unemployment.

This theory also provides a rationale for the puzzling empirical finding from Kroft and Pope

(2014): the AUR is unaffected by an increasing popularity of job-finding websites like Craigslist.

Theoretically, an increasing popularity of this website may reduce the marginal search cost of Craigslist’s

users and incent them to search more intensively. The increase in their search intensity levels does

enhance their relative positions in an intensity ladder. Meanwhile, it creates a negative externality on

the nonusers of Craigslist: their rank declines. While Craigslist may help their users get rid of unem-

ployment faster, it slows the job search process for the nonusers. Overall, the increasing popularity

of job-finding websites has no effect on the AUR.

The magic number of “one-half” is attributed to a statistical property: percentile ranks of any

distribution are uniformly distributed between zero and one, with its average one-half. With the

highest search benefit, the postgraduates tend to search the most intensively and thus rank top in

an intensity ladder. Their percentile rank of search intensity is always one, twice the average of

any economy. Consequently, the postgraduates’ job-finding rate is twice the average, and thus they

always get a job twice as fast as the average. Therefore, the unemployment rate of the postgraduates

4

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is about half the AUR, explaining the puzzling feature of the magic number of “one-half”.4

The success of our theory in explaining the two features suggests that search relativity is one of the

key determinants of a job-finding rate. Since the distributions of search intensity and human capital

in the unemployment are identical in the equilibrium, the distribution of educational level can used

as the proxy for the distribution of human capital (and thus search intensity). This proxy allows us to

derive a novel formula to disaggregate an aggregate unemployment rate into the unemployment rate

by educational attainment without the information on search intensity levels. The formula requires

only two inputs, the AUR and the distribution of educational levels in the labor force, both of which

are easily accessible.

Using the United States Current Population Survey (US CPS) 1994-2015, we disaggregate the

annual AUR into the educational unemployment rates in each of the 50 states. Most of the null

hypotheses, in which the actual and the derived educational unemployment rates are from the same

distribution, cannot be rejected at any conventional level of significance. For example, these null

hypotheses cannot be rejected for high-school graduates and bachelor’s degree holders in 46 and

43 out of 50 states at five percent significance level. Using the least number (two) of the inputs, our

simple formula allows economists, policymakers, and the public to accurately map the AUR to a more

relevant information—the educational unemployment rates. The accuracy of the formula implies that

our model not only explains the two seemingly unrelated features of unemployment qualitatively, but

also predicts the magnitudes of the unemployment rates well over the past two decades.

To the best of our knowledge, there exists no work that documents or explains the two seemingly

unrelated features of unemployment. Cairo and Cajner (2016) is the closest work that studies the

educational unemployment rate. Our paper differs from theirs in the objective. Focusing on the

relationship between the level and the volatility of the unemployment rate, their paper succeeds in

explaining why more-educated workers experience lower unemployment rates and lower employment

volatilities. In contrast, our paper explains the two seemingly unrelated features of unemployment

and how an unemployment distribution emerges, focusing mainly on the relationship between the

AUR and the educational unemployment rate.

Cairo and Cajner (2016) is an extension of the canonical search and matching model with on-

the-job training and endogenous separations. In contrast, our model incorporates search relativity

into the canonical search-theoretic model. Importantly, the derived relation between the AUR and

the educational unemployment rate in our model does not depend on the separation rate. Our work

complements theirs in that the canonical model with search relativity and the endogenous separations,

the key feature in Cairo and Cajner (2016), could explain well both the two seemingly unrelated

features of unemployment and the relation between the level and the volatility of unemployment.

4We realize that the annual salary of the postgraduates, on average, is not the highest in some European countries: theirsearch benefits are not the highest in the unemployment. In this case, their unemployment rates may not be half the AUR.Our theory may still be applicable in the sense that the unemployment rate of any educational group with the highest searchbenefits is half the AUR.

5

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This paper is structured as follows. The basic model environment is described in Section 2.

In Section 3, we characterize the steady-state equilibrium and show that the model captures the two

seemingly unrelated features of unemployment qualitatively. Section 4 evaluates the predictive power

of our model. Section 5 concludes the paper.

2 The Basic Model

This section presents our search relativity theory through the workhorse of a search-theoretic model.

We aim to construct a simple, yet intuitive, model to shed light on the mechanism through which

search relativity affects job-seeking behaviors. Despite the abstraction of other labor market fea-

tures, our model is flexible, could be easily extended to incorporate other features, and, of paramount

importance, captures well the features of unemployment rates.

In this model, time is continuous. There is a continuum of profit-maximizing firms who are risk-

neutral and discount future at a rate r > 0. A firm could be filled by at most one worker, and any

worker can take up at most one position. Since one firm is basically equivalent to one vacancy, we

follow the tradition in this literature to address a firm as a vacancy to avoid confusion.

There is a unit measure of utility maximizing workers who are risk-neutral, infinitely lived, and

share an identical real discounted rate r.5 Each is either employed with earnings w, or unemployed

with home production z > 0.6

Workers are ex ante heterogeneous: they differ in a human capital level δ. We denote by H(δ)

and h(δ) the cumulative distribution function and the corresponding density function of δ. For ease

of exposition, we assume that the distribution is continuous over its support, and the lower support

of H(δ) exceeds home production z so that it makes sense that workers are willing to sign a contract

during a job interview.

We denote by JE(δ) and JU (δ) as the value functions of employment and unemployment. An

employed worker of type δ receives a wage w and faces a separation shock at a Poisson rate λ.

When the shock arrives, the employed worker becomes unemployed. Hence, the value function of

5This simplification is common in this literature (Mortensen and Pissarides, 1994; Moen, 1997; Moscarini, 2005; Roger-son et al., 2005; Gonzalez and Shi, 2010; Fujita and Ramey, 2012; Michaillat, 2012). Applications of the search and matchingmodel also assume agents to be risk-averse such as the literature that investigates the optimal unemployment benefits withsearch frictions (Fredriksson and Holmlund, 2006; Guerrieri et al., 2010). Recent literature also investigates job search be-haviors with the preference of ambiguity aversion (Chan and Yip, 2017). Our model can be easily extended to incorporateagents’ ambiguity aversion; we do not do so because the modification of agents’ preference towards ambiguity complicatesour model without providing a richer economic intuition in our context.

6The model assumes that no decision on labor supply, either the number of working hours or labor force participation, ismade. This simplification is standard (Mortensen and Pissarides, 1994; Shimer, 2005; Hall, 2005; Hagedorn and Manovskii,2008; Hall and Milgrom, 2008; Fujita and Ramey, 2012; Michaillat, 2012), and is in line with empirical regularities: cyclicalvariations in total working hours (unemployment) basically arise from changes in the number of employment but not changesin working hours per worker (labor force participation) (Shimer, 2010).

6

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employment can be written as follows:

rJE(δ) = w(δ) + λ

(JU (δ)− JE(δ)

). (1)

An unemployed worker with home production z > 0 pays a search cost C : R+ 7→ R+ and selects

the optimal level of search intensity s ≥ 0. We assume that search cost is zero in the absence of

search effort, and the search cost function is a strictly increasing strictly convex function. That is,

C(0) = 0, C ′(s) > 0, and C ′′(s) > 0 for all s ≥ 0.

Each transits from unemployment to employment at a rate of F (s)p, where p ∈ (0, 1) measures

the matching technology of an overall economy.7 We can interpret the p as the measure of the eco-

nomic condition so that p is high in booms and low in slumps. In sharp contrast to the existing

literature, the job-finding rate depends on F (s), the cumulative distribution function of search inten-

sity in unemployment, for several reasons. First, F (s) describes the relative position in the search

intensity distribution. Second, it increases in s so that the job-finding rate increases with the relative

position in a search intensity ladder. Third, the lower bound of the F (s) is zero so that the job-finding

rate is zero if no search effort is made. Fourth, its upper bound is one to guarantee that a job-finding

rate F (s)p less than one.

It is noteworthy that the distribution of search intensity F (s) is endogenous. Increasing one’s

search intensity level without climbing up the search intensity ladder does not enhance the likeli-

hood of getting a job. The selection of the optimal search intensity largely depends on the relative

position in the ladder. 8 In the equilibrium, workers’ strategies map their types δ ≥ z to search

intensities s∗(δ) ∈ R+. Hence, unemployed workers of each type choose s to maximize the value of

unemployment given the strategies of other unemployed workers.

Given JE(δ) and others’ strategies, an unemployed worker of type δ chooses his action s to

maximize his value of unemployment as follows:

rJU (δ) = maxs≥0

{z − C(s) + F (s)p

(JE(δ)− JU (δ)

)}. (2)

One may be concerned that workers of different human capital levels may not compete with

one another in a job search process. In reality, jobs are not perfectly segregated by human capital

level. Therefore, it is reasonable that the high-school dropouts and the high-school graduates may

compete for a similar job type, and the bachelor’s degree holders and the postgraduates also perform

a similar task in their positions. Meanwhile, it is rarely to see that the high-school dropouts and the

postgraduates compete for the same job. We will show that each unemployed worker has to consider

7Since endogenizing market tightness does not provide additional economic insight of this paper but significantly com-plicates the analysis, we assume that the job-finding rate does not depend on market tightness. We will discuss this issue inSection 3 and 4.

8Similar to an auction, each unemployed worker submits his own search intensity to bid for a higher job-finding rateF (s)p, and is rewarded with the rate F (s)p.

7

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whether the increase in s improves his relative position in the intensity ladder. In the equilibrium,

workers with a similar human capital level are in a similar position in the intensity ladder; therefore,

workers with a significant difference in a human capital level will not compete with one another in

the equilibrium in deciding ones’ optimal search intensity levels, in line with the reality.

When a vacancy is filled by a worker of type δ, it generates a production value δ and pays a wage

w to the worker of type δ.9 A filled vacancy faces a separation shock at a rate of λ. When the shock

arrives, a filled vacancy becomes unfilled, and receives zero profits. Hence, the asset value of a filled

vacancy JF (δ) can be written as follows:

rJF (δ) = δ − w(δ)− λJF (δ). (3)

Following the existing literature, we assume that wages are determined by maximizing the general-

ized Nash product. Consequently, expected gains from search are split according to the generalized

Nash bargaining solution as follows:

JE(δ)− JU (δ) = β

(JE(δ)− JU (δ) + JF (δ)

), (4)

where β ∈ (0, 1) is a bargaining power of workers. The higher the the β, the higher is workers’

bargaining power. Equating flow in and flow out of unemployment, a steady-state aggregate unem-

ployment rate is given by

λ(1− u) =

∫ ∞z

F (s∗(δ))pdG(δ)︸ ︷︷ ︸Average job-finding Rate

×u, (5)

where G(δ) is the cumulative distribution function of the type of unemployed workers, with g(δ) the

corresponding probability density function. G(δ) is endogenous and, in plain English, captures the

distribution of human capital in the unemployment. The L.H.S. and the R.H.S. of the equation (5) are

the flow in and the flow out of unemployment, where s∗(δ) is the optimal search intensity submitted

by the unemployed worker of type δ, and p∫F (s∗(δ))dG(δ) is the average job-finding rate in the

economy. Similarly, a steady-state unemployment rate of the workers of type δ is given by

λ

(h(δ)− g(δ)u

)= F (s∗(δ))pg(δ)u. (6)

The L.H.S. captures the number of employed workers of type δ flowing into unemployment, where

h(δ)− g(δ)u is the measure of employed workers of type δ. F (s∗(δ))p is the job-finding rate of the

unemployed workers of type δ. So, the R.H.S. captures their flow out of unemployment, where g(δ)u

is the measure of unemployed workers of type δ. In the equilibrium, the flow out and the flow in of

unemployment are equal for workers of each type.

9In fact, the implications of this model do not change if the production value is given by f(δ), where f ′(·) > 0.

8

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3 Characterization of the Steady State Equilibrium

This section characterizes the steady-state equilibrium, explores the mathematical properties of the

equilibrium, and provides economic intuitions as to why the search relativity theory could explain the

two seemingly unrelated feature of unemployment. We begin with the definition of the steady-state

equilibrium.

Definition 1. A steady-state equilibrium is defined as {s(δ), JE(δ), JU (δ), JF (δ), u, g(δ)}, for all

δ ≥ z,

1. (Optimal Search Intensity): s(δ) maximizes JU (δ) given the optimal s∗(δ) of other unemployed

workers;

2. (Value Functions): JE(δ), JU (δ), and JF (δ) satisfy equations (1)-(3);

3. (Rent-Sharing): w(δ) maximizes the generalized Nash product, satisfying the sharing rule (4);

4. (Steady-State Accounting): u and g(δ) satisfy equations (5) and (6).

Using equations (1), (3), and (4), the wage equation is given by

w(δ) = rJU (δ) + β(δ − rJU (δ)). (7)

A wage is equal to an outside option value plus a fraction of economic rent. Using equations (2) and

(7), the outside option value is given by

rJU (δ) = maxs≥0

{z − C(s) + F (s)

βp

r + λ(δ − rJU (δ))

}. (8)

Lemma 1. If δ1 > δ2, s∗(δ1) ≥ s∗(δ2) in a steady-state equilibrium.10

Intuitively, the higher the human capital level, the higher is the bargaining wage due to rent-

sharing. Hence, an unemployed worker with more human capital has a higher net search benefit.

Lemma 1 shows that if the net search benefit is large enough to incent workers of a particular type

to search at s, it is also high enough to incent all other workers with more human capital to search

no less than s. In other words, Lemma 1 implies that all the unemployed workers of type x ≤ δ

will search with the search intensity level s∗(x) not higher than s∗(δ), meaning that the distributions

of human capital in the unemployment and search intensity coincide (i.e., G(δ) = F (s∗(δ))) in the

equilibrium.

Lemma 2. G(δ) = F (s∗(δ)) in a steady-state equilibrium.

Using Lemma 2 and equation (5), the steady-state unemployment rate is given by

u =λ

λ+∫∞z F (s∗(x))pdG(x)

λ+ p∫∞z G(x)dG(x)

λ+ 12p. (9)

10Proof is provided in the Appendix.

9

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Ostensibly, the aggregate unemployment rate (9) is parallel to the one derived from the search and

matching literature: u strictly increases with the job separation rate but decreases with the job-finding

rate.

Using Lemma 2, equation (6), and the aggregate unemployment rate (9), the distribution of human

capital in the unemployment G(δ) is given by

G(δ) =u

2(1− u)

(√1 +

4(1− u)H(δ)

u2− 1

). (10)

Proofs are given in Appendix 6.2. It is noteworthy that G(δ) is endogenous in our model; no further

restriction is imposed on the function G(δ). Being a valid cumulative distribution function, G(δ) has

to satisfy three properties: (i) it increases with δ, (ii) it equals zero at its lower support, and (iii) it

equals one at its upper support. First, differentiating G(δ) with respect to δ, one can show that G(δ)

strictly increases with δ. Second, it is straightforward to verify thatG(δ) approaches zero (one) when

H(δ) approaches zero (one). We can therefore conclude that G(δ) is a valid cumulative distribution

function.

Differentiating both sides of G(δ) = F (s∗(δ)) with respect to δ gives us the corresponding

density function as follows:

g(δ) = f(s∗(δ))ds∗(δ)

dδ. (11)

Differentiating G(δ) with respect to δ and rearranging terms, the unemployment rate associated

with workers of type δ is given by

uδ ≡g(δ)u

h(δ)=

(1 +

4(1− u)H(δ)

u2

)−12

. (12)

Lemma 3. The aggregate unemployment rate u and the unemployment rate of worker of type δ are

given by

u =λ

λ+ 12p

and uδ =

(1 +

4(1− u)H(δ)

u2

)−12

Lemma 3 derives two important formulae of unemployment rates. These two formulae provide

rich intuition on the two seemingly unrelated features of unemployment. The second formula dis-

aggregates the AUR into the unemployment rate of workers of type δ, simply using the distribution

of human capital in the labor force. We will discuss the application of this formula in practice and

evaluate its explanatory power in Section 4.

Using Lemma 3 and equation (10), Lemma 4 follows:

10

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Lemma 4. The unemployment distribution G(δ) is given by

G(δ) =1

2

Ψ(u)

Ψ(uδ),

where Ψ(u)Ψ(uδ)

is the unemployment odds ratio;

Ψ(u) ≡ u1−u is the aggregate unemployment odds; and

Ψ(uδ) ≡ uδ1−uδ is the unemployment odds of workers of type δ.

Proofs are given in Appendix 6.3.

Lemma 4 derives another novel formula of the distribution of human capital in unemployment.

In the equilibrium, the cumulative distribution function of the human capital δ in the unemployment

is half of the unemployment odds ratio of the corresponding type of workers. The formula is surpris-

ingly simple and is again a function of two variables, the AUR and the unemployment rate of workers

of type δ. According to Lemma 3, uδ is a function of the aggregate unemployment rate u and the

distribution of human capitalH(δ). This unemployment distribution is thus a function of u andH(δ)

only. We will evaluate its explanatory power in Section 4.

We proceed to show the existence and the uniqueness of the equilibrium. While Lemma 2 states

that G(δ) = F (s∗(δ)), G(δ) is differentiable from the equation (10). Hence, F (s∗(δ)) is differen-

tiable. Differentiating equation (2) with respect to s and using equations (1) and (7) give the first

order condition as follows.

C ′(s∗(δ))︸ ︷︷ ︸Marginal Search Cost

= f(s∗(δ))βp

r + λ(δ − rJU (δ))︸ ︷︷ ︸

Marginal Search Benefit

. (13)

The optimal search intensity equates a marginal search cost to a marginal search benefit. Using

equations (11) and (13), one could verify that search intensity strictly increases with δ.

ds∗(δ)

dδ=βpg(δ)(δ − rJU (δ))

(r + λ)C ′(s∗(δ))> 0. (14)

Using equations (2), (10), (11), and (12), the optimal s∗(δ) in equation (13) can be found by solving

K(δ) ≡ C(s∗(δ)) in the following first-order linear differential equation:11

dK(δ)

dδ= T (δ)(δ − z) + T (δ)K(δ), (15)

where T (δ) ≡ βph(δ)(r+λ)uΦ1(δ)(1+Φ2(δ)) , Φ1(δ) ≡

√1 + 4(1−u)H(δ)

u2, and Φ2(δ) ≡ βλ

r+λ(Φ1(δ) − 1).

Notice that T (δ) and thus T (δ)(δ − z) are continuous functions on a real line; hence, there exists a

unique solution to this initial value problem with the initial condition K(z) = 0. The unique solution

11The derivation is shown in Appendix 6.4.

11

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to this initial value problem is given by

C(s∗(δ)) =

∫ δ

zT (x′)(x′ − z)e

∫∞x′ T (y)dydx′ ≥ 0.

Since C(s∗(δ)) strictly increases with s∗, the unique s∗ is given by

s∗(δ) = C−1

(∫ δ

zT (x′)(x′ − z)e

∫∞x′ T (y)dydx′

). (16)

Proposition 1. (Existence of the Equilibrium) There exists a unique steady-state equilibrium defined

in Definition 1. The unique strategy profile is given by equation (16). The steady-state AUR and the

unemployment rate associated with each worker type δ are given by Lemma 3. The equilibrium

distribution of human capital in unemployment is given by Lemma 4.

Theorem 1 summarizes five properties of the derived unemployment rates in the steady-state

equilibrium.

Theorem 1. (Properties of Unemployment Rates) In a steady-state equilibrium,

1. uδ unambiguously decreases with δ;

2. the AUR is independent of the distribution of human capital in the labor force H(δ);

3. the lowest uδ equals u/(2− u);

4. a fall in p increases uδ and u for all δ ≥ z; and

5. if 2H(δ)u ( 1

u − 1) > 1, the unemployment rate of workers with a lower human capital level δ

increases more in slumps.

Proof. See the Appendix 6.5.

The First Property. The first statement indicates that the more human capital the worker has,

the lower is his/her unemployment rate. While more-educated workers, on average, possess more

human capital, the unemployment rates, according to this property, are lower at higher educational

levels. This property is supported by the documentation in Figure 1. Since search benefits increase

with human capital, workers with more human capital tend to search more intensively and are thus

more likely to transit into employment. While this implication is seemingly no difference from the

search-theoretic literature, the mechanisms are different. In contrast to this literature, the level of

search intensity essentially plays no role in determining one’s job-finding rate. Instead, a higher

search intensity level places an unemployed worker at a higher position in the intensity distribution.

It is this higher position in the intensity distribution, not the intensity level, that makes him get rid of

the unemployment faster.

The Second Property. It is noteworthy that the AUR is a function of the job separation rate λ and

the matching technology (the economic condition) p of an overall economy, not the distribution of

12

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search intensity or human capital. Mathematically, the AUR is negatively associated with the average

job-finding rate, given by p∫∞z F (s∗(x))dG(x). According to Lemma 2, the distributions of search

intensity and human capital in the unemployment coincide. That is, F (s∗(δ)) = G(δ). The average

job-finding rate reduces to p∫∞z G(x)dG(x). Regardless of the distribution of human capital, the

percentile point follows a uniform distribution with support between zero and one. Since the mean

value of the percentile point is always one half, the average job-finding rate further reduces to p/2,

independent of the distribution of search intensity or human capital.

Consider a worker increases his search intensity level such that his relative position slightly im-

proves. On the one hand, his job-finding rate increases. On the other hand, such the improvement in

the relative position creates a negative externality on others: there exists some unemployed workers

whose relative positions decline. Overall, the average job-finding rate of an economy is unaffected

by the reallocation of the position in the search intensity distribution. This explains why a rise in

one’s search effort could shorten his own average unemployment duration but not the unemployment

spell of the economy as a whole, leaving the AUR independent of the distribution of human capital

or search intensity level. This independence property captures a more general feature of unemploy-

ment than the statistical puzzle of unemployment. While the independence property states that the

AUR is uncorrelated with the distribution of human capital in the labor force, the statistical puzzle

of unemployment documents that the AUR is uncorrelated with the fraction of high-educated work-

ers in the labor force. This property also explains why the natural rate of unemployment remains

steady for quite a long time (at least 50 years in the United States) even though the proportion of

the high-educated increases over several decades (which in turn increases the average human capital

level).

Lastly, one should be aware that it is rather difficult to obtain the information on workers’ search

intensity level (Petrongolo and Pissarides, 2001). We are uncertain how to define and measure search

intensity level in practice. The independence property guarantees that the AUR is free from any

function of search intensity levels, making practitioners easier to uncover the AUR without the infor-

mation on search intensity levels.

The Third Property. This property relates the unemployment rate of workers with the highest

level of human capital to the AUR. Recall from the first property that the unemployment rates are

lower at higher educational levels. Hence, the unemployment rate reaches its minimum when δ tends

to infinity. Using Lemma 3, it is straightforward to show that the lowest unemployment is u/(2− u),

which is about half the AUR.

As indicated in Lemma 1, workers with more human capital tend to search more intensively.

Hence, workers with the highest human capital level will search the most intensively so that they,

once get unemployed, rank top in an intensity ladder (i.e., F (s) = 1). Consequently, their job-

finding rate equals p. As discussed in the first property, the average percentile point of an economy

is always one-half, and thus the average job-finding rate equals p/2. Hence, the unemployed with

the highest human capital get the jobs twice as fast as the average of the economy as to why the

13

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unemployment rate of the postgraduates is about half the aggregate unemployment rate, explaining

the magic number of “one-half”. More strikingly, this result holds regardless of the distribution of

human capital.

The Fourth Property. It is well known that p is low and thus the AUR is high in slumps. This

property states that the unemployment rates are countercyclical regardless of human capital level.

The AUR is countercyclical because it is a weighted average of the unemployment rate of all worker

types, and the unemployment rates of all worker types are countercyclical. This property is supported

by Figure 1: the unemployment rates by educational level move up and down in the same way in the

past 20 years. For example, the unemployment rates are high during 2008-2011 because of the 2008

recession.

The Fifth Property. This property illustrates that the increase in the unemployment rate is more

pronounced for workers with less human capital in slumps. Indeed, a fall in p has two forces on

the unemployment rate. First, a lower p mitigates the marginal effect of the heterogeneity in the

search relativity F (s∗(δ)), closing the gaps in the job-finding rates and thus the unemployment rates

between workers of any two types. Second, the heterogeneity in the unemployment rate arises not

from any heterogeneity in the employment but from the heterogeneity in the search relativity in the

unemployment. While the unemployment rates are higher at lower educational levels, the propor-

tion of unemployment is larger among less-educated workers. Hence, the impacts of a lower p are

more pronounced on the less-educated. If 2H(δ)u ( 1

u − 1) > 1, the former effect will be dominated.

Therefore, the increase in the unemployment rate of workers with a lower δ is more pronounced in

slumps.

Clearly, the first three properties of unemployment in Theorem 1 correspond to the two seemingly

unrelated features of unemployment. While the implications of the fourth and the fifth property are

easily seen in Figure 1, we do not discuss it in details. Instead, we relegate to the online Appendix B

the evidence that the unemployment rates are higher in slumps and the effects are more pronounced

for less-educated workers.

However, the fifth property is valid only if 2H(δ)u ( 1

u − 1) holds. The remaining question is how

likely this inequality holds. Notice that 2H(δ)u ( 1

u − 1) strictly increases with H(δ) and decreases

with u. According to the US CPS data, the proportions of high-school graduates or below followed a

decreasing trend and reached its lowest point at 34% in 2015. According to Bureau of Labor Statistics

Data, the highest recorded monthly unemployment rate (since 1948) was 10.8% in November and

December in 1982. With H(δ) = 34% and u = 10.8%, 2H(δ)u ( 1

u − 1) should exceed 52, far above

one. In other words, the smallest value of 2H(δ)u ( 1

u − 1) exceeds 52 during 1948-2015. In fact,

this inequality holds even if the share of high-school graduate or below H(δ) is as low as 5% and

the unemployment rate is as high as 25%. Following the current decreasing trend in the share of

high-school graduate or below (minus 1% each year), we expect that the condition holds not only

during 1948-2015 but also the coming thirty years or even more. In other words, the fifth property

in Theorem 1, together with the other properties, is expected to hold in the United States during

14

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1948-2045.

Up to this point, this paper has demonstrated the explanatory power of the search relativity theory.

It is noteworthy that our slight modification of the search-theoretic model is indeed widely applicable.

We purposely abstract other labor market features for ease of exposition; we present a model with

minimal labor market features to shed light on the crucial role of the search relativity in explaining

the heterogeneity in the unemployment rate by educational attainment. Our theory, though simple,

does qualitatively capture the two seemingly unrelated features of unemployment (Property 1-3) and

the dynamics of the unemployment rate over business cycle (Property 4 and 5), suggesting that the

search relativity is a key determinant of the job-finding rate.

We close this section with several remarks. First, Theorem 1 is robust to heterogeneous separation

rates λ. More-educated workers tend to have lower separation rates (Cairo and Cajner, 2016). Hence,

they have higher values of employment and thus higher search benefits. Consequently, Lemma 2 and

thus the following lemmas and theorem hold even though the separation rate is endogenous. Second,

some may interpret z as an unemployment insurance. If z equals a fraction of a wage, search benefits

JE(δ) − JU (δ) are higher for the more-educated even though both their values of employment and

unemployment are higher. Again, Lemma 2 holds and Theorem 1 is robust to heterogeneous home

production values. To verify the credibility of the search relativity theory, we evaluate the predictive

power of the model in the next section.

4 The Evaluation of the Search Relativity Theory

This section purposes to assess the predictive power of the search relativity model beyond the two

seemingly unrelated features of unemployment. In particular, this section evaluates the unemploy-

ment distribution G(δ) implied by Lemma 4 and the unemployment rate by educational attainment

uδ implied by Lemma 3. In the end of this section, we derive a measure of the unemployment sheerly

generated by search friction, in which we call it fundamental frictional unemployment rate. We will

show that search relativity explains most of the unemployment rate (if not considered entirely) that

is generated by search friction, leaving no room that can be explained by the level of search inten-

sity. Throughout this section, the implications are evaluated using the US CPS 1994-2015, and the

samples of examination are restricted to the labor force aged 25-60.

These exercises are important for two reasons. First, one may wonder that the proposed theory of

this paper—Search Relativity Theory—explains the two seemingly unrelated features of unemploy-

ment by chance. The predictive power of the search relativity model does reflect the credibility of the

theory. In other words, this exercise provides additional support on the search relativity theory if the

predictive power of the model is sufficiently high. Second, Lemma 3 and 4 provide two novel for-

mulas of the unemployment rate by educational attainment and the unemployment distribution: the

lemmas provide closed-form expressions linking the two variables to the aggregate unemployment

rate and the distribution of human capital. If the proposed procedures to obtain the unemployment

15

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distribution and the unemployment rate by educational attainment are sufficiently easy to implement

without solving systems of equations, the two formulas can then be widely and directly applied in

other contents. Undoubtedly, such the applications hinge on the accuracy of the two formulas. The

evaluations in this section speak directly to the concern of its accuracy.

Analogue to the level of search intensity, it is an empirical challenge in observing and measuring

the relative position of search intensity amongst unemployed workers. Thanks to Lemma 2, we show

that the distributions of search intensity and human capital in the unemployment coincide in the

equilibrium. Thus, Lemma 3 and 4 could make use of the distribution of human capital to measure

the search relativity and derive the formula of the unemployment rate by educational attainment and

the unemployment distribution. In practice, it may also be difficult to observe the exact human capital

level of a worker. We therefore make two assumptions:

Assumption 1. A human capital level strictly increases with educational attainment.

Assumption 2. A human capital distribution is continuous over its support.

We denote by j the educational level: the higher the number of j the higher is the educational

level. Here, an educational level is called higher if the average wage associated to this educational

level is higher during 1994-2015 in the United States so that Assumption 1 is satisfied. We denote

by δ̄j and δj as the highest and the lowest human capital level in the educational group j. Also, we

also denote by Hj as the cumulative distribution function of a worker of type δ̄j in the educational

group j. Assumption 1 implies that δj+1 > δ̄j , and Assumption 2 ensures that given any j, for

every ε > 0 there exists a η > 0 such that |δj+1 − δ̄j | < η implies |H(δj+1) − H(δ̄j)| < ε.

With these assumptions, we now proceed to evaluate the implied unemployment distribution and the

unemployment rate by educational attainment.

4.1 The Evaluation of the Unemployment Distribution

This subsection discusses the unemployment distribution derived from the model. According to

Lemma 4, G(δ) is the cumulative distribution function of human capital in the unemployment, which

is indeed the unemployment distribution across educational groups. For theoretical convenience, the

expression in Lemma 4 is not ready for the implementation. This subsection will derive the formula

that allows economists, policymakers, and the public to generate the unemployment distribution in

practice.

Theorem 2. (Unemployment Distribution) Suppose Assumption 1 and 2 are satisfied. In a steady-

state equilibrium, the cumulative distribution function of the educational group j in the unemploy-

ment Gj is given by

Gj =u

2(1− u)

(√1 +

4(1− u)Hj

u2− 1

).

16

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Figure 3: The Predicted and the Actual Unemployment Distribution in the United States

020

4060

8010

0Pr

edic

ted

Une

mpl

oym

ent D

istri

butio

n (in

%)

1994 2000 2005 2010 2015Year

HSD HS AD BA PG 020

4060

8010

0Ac

tual

Une

mpl

oym

ent D

istri

butio

n (i

n %

)

1994 2000 2005 2010 2015Year

HSD HS AD BA PG

Notes: The left (right) figure displays the predicted (actual) unemployment distribution in the United States. Each line indi-cate the cumulative distribution function of the corresponding educational group in the unemployment. HSD, HS, AD, BA,and PG. represent the high-school dropouts, the high-school graduates, individuals with some college education and asso-ciate’s degree holders, bachelor’s degree holders, and the postgraduates., respectively. Each dot illustrates the unemploymentdistribution in the corresponding year. Data are collected from the Current Population Survey 1994-2015 and samples arerestricted to labor force participants aged 25-60.

This theorem derives a novel formula of the unemployment distribution across educational lev-

els. We proceed to verify the predictive power of Gj . According to Theorem 2, the unemployment

distribution is a function of two variables: the aggregate unemployment rate u and the cumulative

distribution function of educational level Hj , both of which are easily obtained from the US CPS.

The predicted and the actual annual Gj are illustrated in Figure 3. As highlighted before, Gjis one for the most productive workers; therefore, it must be identical to the actual Gj for the post-

graduates. The predicted Gj for the associate’s degree holders and the bachelor’s degree holders are

nearly identical to the actual ones over twenty years. However, the predicted Gj’s are about 5-10

percent higher than the actual ones for high-school dropouts and high-school graduates. One of the

possibilities, accounting for the derivation, is that low-educated unemployed workers may decide not

only on their search intensity level, but also on whether to participate to the labor force. Nevertheless,

our model did not explicitly endogenize the decision on the labor force participation and we leave it

for future research avenue.12 This result does provide a solid support that the implied unemployment

distribution from the search relativity model largely coheres with the data. To further illustrate the

performance of this novel formula, we treat each state as a local labor market and conduct the same

exercise in each of the 50 states in the United States. The predicted and the actual values of Gj in

each state are illustrated in the Online Appendix C. Surprisingly, the predictabilities of Theorem 2 in

most of the states are as good as its performance in the country as a whole. We therefore conclude

12For example, incorporating the search relativity in the framework of Alvarez and Shimer (2011) could be a fruitful andinteresting research area.

17

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that the prediction of Theorem 2 on the unemployment distribution is fairly good.

4.2 The Unemployment Rate by Educational Attainment

This subsection purposes to assess the predictive power of the formula of the unemployment rate by

educational attainment implied by Lemma 3. For theoretical convenience, the expression in Lemma 3

is not ready for the implementation. This subsection will derive the formula that allows economists,

policymakers, and the public to generate the unemployment rate of various educational groups in

practice. In particular, the expression in Lemma 3 maps an aggregate unemployment rate to the

unemployment rate of the xth percentile of a human capital distribution. But the percentile of each

respondent is unobservable in data. The following theorem presents a disaggregation theory that

allows us to generate the unemployment rates of various educational groups under mild assumptions.

Theorem 3. (Disaggregation Theory) Suppose Assumption 1 and 2 are satisfied. In a steady-state

equilibrium, the unemployment rate of the educational group j is given by

uj =2u

(Bj +Bj−1)(17)

where Bj ≡ (u2 + 4(1− u)Hj)12

Proof. See the Appendix 6.6.

Using the US CPS, we generate the actual and the predicted unemployment rates of high-school

graduates, individuals with some college education and associate’s degree holders, bachelor’s degree

holders, and the postgraduates. Figure 4 displays both the actual (the solid lines) and the predicted

(the dash lines) annual unemployment rates of various educational groups over 1994-2015. According

to Theorem 1, the implied unemployment rates of various educational groups do capture the two

seemingly unrelated features of unemployment and the movement over business cycle. It is therefore

expected that the two sets of values display similar movements over time regardless of educational

attainment. More strikingly, the magnitude of the actual and the predicted unemployment rates are

so close that the null hypothesis that they are drawn from an identical distribution cannot be rejected

by the Wilcoxon rank-sum test for the high-school graduates, the bachelor’s degree holders, and

the postgraduates. Certainly, the disaggregation theory does a superb performance in mapping the

aggregate unemployment rate into the unemployment rate by educational attainment in magnitude in

the United States. Although the null hypothesis is rejected for the sample of individuals with some

college education and associate’s degree holders, the predicted values do display a co-movement with

the actual ones over the entire period of examination.

Again, to provide a further support on Theorem 3, we apply this disaggregation theory to disaggre-

gate the annual aggregate unemployment rates to the unemployment rates of high-school graduates,

associate’s degree holders, bachelor’s degree holders, and postgraduates in each state during 1994-

2015. Both the actual (the solid lines) and the predicted (the dash lines) annual unemployment rates

18

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Figure 4: Evaluation of the Disaggregation Theory

02

46

810

12U

nem

ploy

men

t Rat

e (in

%)

1994 2000 2005 2010 2015Year

p-value=0.32

High-School Graduates

02

46

810

12U

nem

ploy

men

t Rat

e (in

%)

1994 2000 2005 2010 2015Year

p-value=0.00

Some College & Associate's Degree Holders

02

46

810

12U

nem

ploy

men

t Rat

e (in

%)

1994 2000 2005 2010 2015Year

p-value=0.42

Bachelor's Degree Holders

02

46

810

12U

nem

ploy

men

t Rat

e (in

%)

1994 2000 2005 2010 2015Year

p-value=0.17

Postgradrates

Notes: This figure displays the predicted unemployment rate (the dotted line) and the actual unemployment rate (the solidline). The predicted unemployment rate is simulated using Theorem 3. Data are from the US CPS. Samples are restricted tothe labor force aged 25-60.

19

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27)

04812 1994

2000

2005

2010

2015

Stat

e: IA

(p-v

alue

=0.7

4)

04812 1994

2000

2005

2010

2015

Stat

e: ID

(p-v

alue

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5)

04812 1994

2000

2005

2010

2015

Stat

e: IL

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04812 1994

2000

2005

2010

2015

Stat

e: IN

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04812 1994

2000

2005

2010

2015

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e: K

S (p

-val

ue=0

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04812 1994

2000

2005

2010

2015

Stat

e: K

Y (p

-val

ue=0

.22)

04812 1994

2000

2005

2010

2015

Stat

e: L

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-val

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.08)

04812 1994

2000

2005

2010

2015

Stat

e: M

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-val

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04812 1994

2000

2005

2010

2015

Stat

e: M

D (p

-val

ue=0

.36)

04812 1994

2000

2005

2010

2015

Stat

e: M

E (p

-val

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04812 1994

2000

2005

2010

2015

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e: M

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e=0.

67)

04812 1994

2000

2005

2010

2015

Stat

e: M

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04812 1994

2000

2005

2010

2015

Stat

e: M

O (p

-val

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04812 1994

2000

2005

2010

2015

Stat

e: M

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es:

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ure

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20

Page 22: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

Figu

re4:

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2005

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2005

2010

2015

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e: N

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04812 1994

2000

2005

2010

2015

Stat

e: N

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2005

2010

2015

Stat

e: N

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2005

2010

2015

Stat

e: N

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2000

2005

2010

2015

Stat

e: N

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2005

2010

2015

Stat

e: N

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2000

2005

2010

2015

Stat

e: N

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-val

ue=0

.32)

04812 1994

2000

2005

2010

2015

Stat

e: N

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04812 1994

2000

2005

2010

2015

Stat

e: O

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-val

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.56)

04812 1994

2000

2005

2010

2015

Stat

e: O

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-val

ue=0

.34)

04812 1994

2000

2005

2010

2015

Stat

e: O

R (p

-val

ue=0

.64)

04812 1994

2000

2005

2010

2015

Stat

e: P

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.32)

04812 1994

2000

2005

2010

2015

Stat

e: R

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42)

04812 1994

2000

2005

2010

2015

Stat

e: S

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-val

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04812 1994

2000

2005

2010

2015

Stat

e: S

D (p

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ue=0

.51)

04812 1994

2000

2005

2010

2015

Stat

e: T

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04812 1994

2000

2005

2010

2015

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e: T

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04812 1994

2000

2005

2010

2015

Stat

e: U

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04812 1994

2000

2005

2010

2015

Stat

e: V

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.85)

04812 1994

2000

2005

2010

2015

Stat

e: V

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04812 1994

2000

2005

2010

2015

Stat

e: W

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2005

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2015

Stat

e: W

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2005

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e: W

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2005

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21

Page 23: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

Figu

re6:

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2005

2010

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e: A

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e: A

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2005

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e: C

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2000

2005

2010

2015

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e: D

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04812 1994

2000

2005

2010

2015

Stat

e: F

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2000

2005

2010

2015

Stat

e: G

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2000

2005

2010

2015

Stat

e: H

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04812 1994

2000

2005

2010

2015

Stat

e: IA

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04812 1994

2000

2005

2010

2015

Stat

e: ID

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04812 1994

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2005

2010

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Stat

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2005

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2005

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2010

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2005

2010

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22

Page 24: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

Figu

re5:

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e: N

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e: N

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Page 25: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

Figu

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24

Page 26: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

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Page 27: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

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Page 28: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

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27

Page 29: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

of 1994-2015 are plotted in the Figure 5-8. According to these figures, the observed and the predicted

unemployment rate are close in its magnitude for most of the educational groups and states.

We perform the Wilcoxon rank-sum test for each of the educational groups in each state and

report the associated p-value. Most of the tests cannot reject the null hypothesis that the actual and

the predicted unemployment rates are from an identical distribution. In particular, the null hypothesis

cannot be rejected at one percent level in all of the 50 states for the high-school graduates. Meanwhile,

we cannot reject the null hypothesis in 48 and 39 out of 50 states for bachelor’s degree holders and

the postgraduates. At the conventional significance level (five percent level), we cannot reject the

null hypothesis in over half the United States in these three educational groups. Surprisingly, the

null hypothesis cannot be rejected over half the U.S. for high-school graduates, bachelor’s degree

holders, and postgraduates at 10 percent significance level. More strikingly, in the group of high-

school graduates and bachelor’s degree holders, the null hypothesis cannot be rejected in about half

the United States at 50 percent significance level. These results strongly suggest that the derived

formula (3) performs so well (if not considered as nearly perfectly) in predicting the magnitudes

of the unemployment rate by educational attainment that most of the tests could not reject the null

hypothesis that the derived formula (3) is identical to the underlying data generating process of the

unemployment rate by educational attainment. However, one should be aware that even though the

predicted and the actual values display a close co-movement for the sample of associate’s degree

holders, the accuracy in predicting the magnitude is not as satisfactory as that in other educational

categories. We leave further investigation on this issue for future avenue.

With the superb performance of the search relativity theory, the disaggregation theory in Theorem

2 and Theorem 3 could be widely applied to map the aggregate unemployment rate in the unemploy-

ment distribution and the unemployment rates of the educational groups of interest. But in addition to

the predictability of a formula, there are three other criteria one should be concerned in constructing

a formula, namely the number of input variables, the accessibility of the inputs, and the easiness of

implementation.

First, our theory utilizes the least number of input variables. Conditional on the predictability,

the less the input variables, the better is the theory. To disaggregate the aggregate unemployment

rate, at least two variables are required because the aggregate unemployment rate is identical across

the educational groups. According to Theorem 2 and Theorem 3, the unemployment distribution

and the unemployment rate by educational attainment are functions of two variables: the aggregate

unemployment rate and the cumulative distribution function of educational attainment, free from

other parameters. Hence, our theory requires the least number of input variables.

Second, the accessibility of input variables is also an issue: a theory is useful only if the required

underlying conditions or the input variables are observable. Our theory requires the aggregate unem-

ployment rate and the distribution of educational attainment. Needless to mention, these two variables

are well defined and easily accessible in all developed countries and in most (if not all) developing

ones. On the contrary, it is rather challenging to obtain the information on an individual’s search

28

Page 30: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

intensity level, the functional form of a matching function, and a job separation rate. Undoubtedly,

our formulas are superior to others (if others exist) in the accessibility of its inputs.

Third, our formulas are not computer-intensive. Unlike many nowadays fancy estimation or cal-

ibration methods, our formulas involve no recursive structure, systems of equations, or samples of

an enormous number of observations. Indeed, the computation takes almost no time and is easy to

implement for economists, policymakers, and even the public.

Of course, with these three advantages, the predictability of the formulas is our concern. As

demonstrated, not only the predicted and the actual values display a similar movement over time, but

also the Wilcoxon rank-sum test of equality cannot reject most of the null hypotheses that the actual

and the observed values are drawn from the same distribution at any conventional significance level in

almost all the states. We conclude that our theory succeeds not only in explaining the two seemingly

unrelated features of unemployment but also in mapping the aggregate unemployment rate into the

unemployment distribution and the unemployment rate of each educational attainment in at least four

aspects: its predictability, its least number of input variables, its accessibility of the required inputs,

and its easiness of implementation.13

According to the steady-state accounting equation (6), the heterogeneity in the unemployment

rate stems from the differences in the job-finding rate and/or the separation rate. We abstract many

labor market features to shed light on the crucial role of the search relativity in explaining the differ-

ence in the unemployment rate by educational attainment. For example, workers share an identical

job separation rate λ and economic environments, including the economic condition p, the wage

determination method, and workers’ bargaining power β etc. Therefore, the heterogeneity in the un-

employment rates must result from the difference in the job-finding rate. Since we shut down the

channel in which the level of search intensity may increase the job-finding rate, the heterogeneity in

the unemployment rates is solely attributed to search relativity. In other words, the unemployment

distribution is generated by search relativity in our model. The gaps between the actual and the pre-

dicted unemployment rates of various educational groups are therefore attributed to the differences in

labor market features other than search relativity. The superb performances of Theorem 2 and The-

orem 3 suggest that it is the search relativity, not the level of search intensity, the separation rate, or

the market structure, that generates the heterogeneity in the unemployment rates across educational

groups.

4.3 Fundamental Frictional Unemployment Rate

In this subsection, we discuss another disaggregation theory of the search relativity model: the mea-

sure of the fundamental frictional unemployment rate (FFUR). Here, we define the FFUR as the

unemployment rate that associates with the unemployment spell that cannot be further shortened by

13The authors also verified that the formula works well using Canadian Labour Force Survey 1994-2015 and the UnitedKingdom Labour Force Survey 1994-2015. Testing the implications of the search relativity model in other OECD countrieswill definitely be a fruitful research avenue.

29

Page 31: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

increasing one’s search intensity or human capital. This subsection asks if workers keep increasing

their search intensity and/or human capital, does their unemployment rate approach zero? In other

words, if search cost is sufficiently low and human capital is sufficiently high, does search frictional

unemployment vanish? If not, what will be the frictional unemployment rate, abstracting the factors

of search effort and human capital?

According to the search relativity theory, those with the highest human capital level should search

the most intensively. Workers with the highest human capital level always ranks top in a search in-

tensity ladder. Further increasing his search intensity and human capital will not increase his relative

position and thus the job-finding rate. With the highest human capital level in the economy, their

unemployment rate in principle sheerly arises from search friction, net of search effort and human

capital. In other words, their unemployment rate remains at the FFUR even though they further

increase their human capital and search intensity.

Using Lemma 3, when H(δ) approaches one, uδ equals u/(2 − u), which is the FFUR. The

FFUR can therefore be interpreted as the efficiency of the matching technology (i.e., the friction) in

the labor market. The lower is the FFUR, the more efficient is the labor market in the job-seeking

process. Truly, to conclude whether a higher natural rate of unemployment is attributable to the

inefficient matching technology or the lack of workers’ search effort is rather hasty. The derived

FFUR plays its role in establishing a positive relationship between the aggregate unemployment rate

and the efficiency of a matching technology. As the FFUR strictly increases with u, we confirm that

a lower natural rate of unemployment does reflect a more efficient matching technology in the labor

market. More importantly, using u/(2− u), the frictional unemployment rate, though unobservable,

can be quantified.

In fact, if the share of the educational group j with the highest human capital level is small

enough, Hj approaches one. If Assumption 1 is satisfied, the postgraduate workers are the ones with

the highest human capital level. With the following assumption, the FFUR is approximately equal to

the unemployment rate of the postgraduates.

Assumption 3. The share of the postgraduates is sufficiently small.

Theorem 4. (Disaggregation Approximation Theory) Suppose Assumption 1 and 3 are satisfied.

In a steady-state equilibrium, the unemployment rate of the postgraduates approximately equals the

FFUR, given by u/(2− u).

This disaggregation approximation theory shows that the unemployment rate of the postgraduates

equals the FFUR, which is a function of the aggregate unemployment rate only. We evaluate this ap-

proximation theory by comparing the FFUR with the actual unemployment rate of the postgraduates.

If the two sets of values are different, we should cast doubt on our arguments in the previous section

that the search relativity, not the level of search intensity, is a key determinant of the job-finding rate

and is the major source of the unemployment distribution.

Figure 9 shows that the FFUR and the actual unemployment rates of the postgraduates exhibit

a similar movement both in recession and expansion. The two sets of values are so close that they

30

Page 32: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

overlap for ten consecutive years during 1995-2004. However, the FFURs are slightly higher than the

actual unemployment rate in slumps during 2008-2010. With the exception of the fair performance

in slumps, the approximation method basically performs well in capturing the unemployment rate of

the postgraduates over the past two decades.

Figure 9: Evaluation of Fundamental Frictional Unemployment Rate

02

46

810

12U

nem

ploy

emnt

Rat

e (in

%)

1994 2000 2005 2010 2015Year

Actual Unemployment Rate of the PostgraduatesFFUR

p-value=0.26

Fundamental Frictional Unemployment Rate

Notes: This figure displays the FFUR (the dotted line) and the actual unemployment rate of the postgraduates (the solid line).The FFUR is simulated using Theorem 4. Data are from the US CPS. Samples are restricted to the labor force aged 25-60.

We again generate the FFUR and the unemployment rates of the postgraduates by state and per-

form the the Wilcoxon rank-sum tests in each state. We present the two sets of variables in Figure

10. This exercise is astonishing because the FFUR and the unemployment rates of the postgraduates

are so close that the null hypothesis, that the two sets of values are from an identical distribution,

cannot be rejected in 70 percent of the States at five percent significance level. We cannot reject the

hypothesis in over half the United States at 25 significance level. With only one input variable, the

predictive power of the disaggregation approximation theory is exceptionally high. Moreover, this

approximation theory preserves all the advantages of the disaggregation theory: its predictability, its

least number of input variables, its accessibility of the required input, and its easiness of implemen-

tation. Nevertheless, the drawback of this theory is that it can only be applied to the postgraduates,

not the other educational categories.

Notice that the FFUR is derived by assuming that a job-finding rate is a function of search rel-

ativity. Suppose both ones’ job-finding rate is strictly increasing in both the level and the relative

position of search intensity. The unemployment spell for the postgraduates is expected to be shorter

than the one associated with the FFUR. That is, if the level of search intensity also plays a role in

determining one’s job-finding rate, the unemployment rate of the postgraduates in principle should be

lower than the FFUR. According to Figure 9, the two sets of values are so close that the statistical test

31

Page 33: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

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Page 34: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

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Stat

e: O

R (p

-val

ue=0

.56)

04812 1994

2000

2005

2010

2015

Stat

e: P

A (p

-val

ue=0

.64)

04812 1994

2000

2005

2010

2015

Stat

e: R

I (p-

valu

e=0.

21)

04812 1994

2000

2005

2010

2015

Stat

e: S

C (p

-val

ue=0

.00)

04812 1994

2000

2005

2010

2015

Stat

e: S

D (p

-val

ue=0

.62)

04812 1994

2000

2005

2010

2015

Stat

e: T

N (p

-val

ue=0

.05)

04812 1994

2000

2005

2010

2015

Stat

e: T

X (p

-val

ue=0

.29)

04812 1994

2000

2005

2010

2015

Stat

e: U

T (p

-val

ue=0

.67)

04812 1994

2000

2005

2010

2015

Stat

e: V

A (p

-val

ue=0

.57)

04812 1994

2000

2005

2010

2015

Stat

e: V

T (p

-val

ue=0

.89)

04812 1994

2000

2005

2010

2015

Stat

e: W

A (p

-val

ue=0

.36)

04812 1994

2000

2005

2010

2015

Stat

e: W

I (p-

valu

e=0.

11)

04812 1994

2000

2005

2010

2015

Stat

e: W

V (p

-val

ue=0

.00)

04812 1994

2000

2005

2010

2015

Stat

e: W

Y (p

-val

ue=0

.24)

Not

es:

Thi

sfig

ure

disp

lays

the

FFU

R(t

hedo

tted

line)

and

the

actu

alun

empl

oym

entr

ate

ofth

epo

stgr

adua

tes

(the

solid

line)

.T

heFF

UR

issi

mul

ated

usin

gT

heor

em4.

Dat

aar

efr

omth

eU

SC

PS.S

ampl

esar

ere

stri

cted

toth

ela

borf

orce

aged

25-6

0.

33

Page 35: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

could not reject the null hypothesis that the derived FFUR is identical to the underlying data gener-

ating process of the actual unemployment rates of the postgraduates at any conventional significance

level. It basically leaves no room that can be explained by the level of search intensity. However,

the actual unemployment rates are indeed slightly lower than the FFUR in slumps. One of the possi-

bilities is that the unemployment rate in this period is not only generated by search friction, but also

by rationing unemployment (Michaillat, 2012) and ambiguity unemployment (Chan and Yip, 2017),

both of which are shown to play a crucial role in determining the unemployment rate in economic

downturns.

Therefore, this section not only illustrates the three applications of the search relativity model

but also points to two conclusions. First, while the search relativity is the key determinants of the

job-finding rate, the possibility that the level of search intensity matters in determining the transition

rate is at best low. Second, the search relativity is the major source of unemployment distribution.

5 Conclusion

This paper documents two puzzling phenomena of unemployment, namely the two seemingly unre-

lated features of unemployment. We propose a unified theory to explain the features through the

canonical search and matching model with search relativity. Our model derives the novel formu-

las for the unemployment distribution, the unemployment rate by educational attainment, and the

fundamental frictional unemployment rate, each of which are shown to cohere with the data. The

superb performances in these formulas suggest that the search relativity is the key determinant of the

job-finding rate and is the major source contributing the heterogeneity in the unemployment rate.

This paper brings a new research direction in several aspects. First, this paper succeeds in disag-

gregating the aggregate unemployment rate into the unemployment rate by education attainment. It

will be fruitful and interesting to disaggregate the aggregate unemployment duration into the unem-

ployment duration by educational attainment if the implied duration is derived by a search relativity

model. Second, we show that the formulas fit the US data well. It is a fruitful area to test whether our

search relativity model works well with European labor markets. Third, the proposed theory embeds

the search relativity in a random search model. Incorporating the relativity in a directed search model

with on-the-job search allows the model to capture the on-the-job transition. Such the generalization

completes our understanding in the job-seeking behaviors among both the unemployed and the em-

ployed. Fourth, little is known about the responsiveness of the unemployment rate by educational

attainment over business cycle. To explore the elasticity of the unemployment rate of each educa-

tional attainment with respect to the aggregate unemployment rate will be a fruitful and interesting

area.

34

Page 36: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

6 Appendix: Proof

6.1 Proof of Lemma 1

Denote Φ(δ) as βpr+λ(δ − rJU (δ)). If ∂Φ(δ)/∂δ ≤ 0, then ∂rJU (δ)/∂δ ≥ 1. Applying the envelope

theorem to equation (8), ∂Φ(δ)/∂δ ≤ 0 implies that ∂rJU (δ)/∂δ ≤ 0. A contradiction results.

Hence, we can conclude that ∂Φ(δ)/∂δ > 0. We now prove that s∗(δ1) ≥ s∗(δ2) by contradiction.

Suppose it is not the case. Given δ1 > δ2, there exists a steady-state Nash equilibrium such that

s1 < s2, where si is denoted as the optimal search intensity of the worker of type δi. Workers of type

δ2 picks s2 because F (s2)Φ(δ2)− C(s2) ≥ F (s1)Φ(δ2)− C(s1). Therefore, we have

(F (s2)− F (s1))Φ(δ2) ≥ C(s2)− C(s1)

(F (s2)− F (s1))Φ(δ1) > C(s2)− C(s1)

F (s2)Φ(δ1)− C(s2) > F (s1)Φ(δ1)− C(s1)

The second inequality arises because Φ(δ) is strictly increasing in δ and δ1 > δ2. According to the

last inequality, it is strictly better off for workers of type δ1 to choose s2 instead of s1. Therefore, we

can conclude that s∗(δ1) ≥ s∗(δ2) if δ1 > δ2 in a steady-state Nash equilibrium.

6.2 The Derivation of Equation (10)

Notice that G(δ) and F (s∗(δ)) are two endogenous variables. Lemma 2 ensures that these two

variables are equal in the steady-state equilibrium. Nevertheless, the lemma does not specify the

functional form of the two distributions. We conjecture that G(δ) is a differentiable function of δ and

verify this claim later.

Using equation (6), G(δ) is the solution of the following differential equation.

G′(δ)u =λh(δ)

λ+G(δ)p(18)

Notice that u is shown to be independent of δ. Rearranging terms, we have

(λ+G(δ)p)G′(δ)u = λh(δ)

Integrating both side from z to x, we have

u

∫ x

zλ+G(δ)pdG(δ) =

∫ x

zλh(δ)dδ

uλG(δ) + up

∫ x

zG(δ)dG(δ) = λH(x)

upG2(δ)

2= λ(H(δ)−G(δ)u)

35

Page 37: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

Solving the quadratic equation gives the solution of G(δ) as in equation (10). Notice that G(δ) is a

differentiable function.

6.3 Proof of Lemma 4

Using Lemma 3 and equation (10), we have

G(δ) =u

2(1− u)

(√1 +

4(1− u)H(δ)

u2− 1

)

=1

2

u

1− u

(1

uδ− 1

)=

1

1− uδuδ

=1

2

Ψ

Ψδ

=1

2Θδ

6.4 The Derivation of Equation (15)

Using F (s∗(δ)) = G(δ) and equation (10),

F (s∗(δ))βp

r + λ=

βλ

r + λ(Φ1(δ)− 1) (19)

where Φ1(δ) =

√1 + 2pH(δ)

λu . Using equations (8) and (19), we have

δ − rJU (δ) =δ + C(s∗(δ))− z

1 + Φ2(δ)

where Φ2(δ) = βλ(Φ1(δ)−1)r+λ . Substituting the above equation, f(s∗(δ))ds∗(δ)/dδ = g(δ) and equa-

tion (12) into equation (13), we have

dC(s∗(δ))

dδ= C ′(s∗(δ))

ds∗(δ)

dδ=

h(δ)

uΦ1(δ)

βp

r + λ

δ + C(s∗(δ))− z1 + Φ2(δ)

= T (δ)(δ − z) + T (δ)C(s∗(δ))

which can be written as equation (15).

6.5 Proof of Theorem 1

Differentiating uδ in Lemma 3 with respect to δ, we have

duδdδ

= −2(1− u)h(δ)

u2

(1 +

4(1− u)H(δ)

u2

)−32

< 0

36

Page 38: Ying Tung Chan and Chi Man Yip · 11/23/2018  · Ying Tung Chan and Chi Man Yip Abstract Why are the unemployment rates lower at higher educational levels? Why is the aggregate unem-ployment

Differentiating the above derivative with respect to u, we have

d2uδdudδ

= −u+ 2(1− u)

u(1− u)

2H(δ)(1− u)− u2

u2 + 4(1− u)H(u)

d2uδ/dudδ > 0 iff 2H(δ)(1− u) < u2.

6.6 Proof of Theorem 3

uj = E(u(δ)

∣∣∣∣δj ≤ δ ≤ δ̄j)

=

∫ δ̄jδju(δ)h(δ)dδ

Hj −Hj−1

=

∫ δ̄jδj

(1 + 4(1−u)H(δ)

u2

)−12h(δ)dδ

Hj −Hj−1

=

∫ HjHj−1

(1 + 4(1−u)x

u2

)−12dx

Hj −Hj−1

=u

Hj −Hj−1

∫ Hj

Hj−1

(u2 + 4(1− u)x

)−12 dx

=u

Hj −Hj−1

1

4(1− u)

∫ Bj

Bj−1

y−12 dy

=u

Hj −Hj−1

1

2(1− u)y

12

∣∣∣∣BjBj−1

=2u

(B12j +B

12j−1)

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