Preliminary  results    

Dung  Doan  

Crawford  School  of  Public  Policy  27  November  2012

Income and diet quality in China2004-2009

Research context   Structural shift in dietary consumptions in developing

countries   Characterized not by calories deficiency, but by unbalanced diet   Significant impacts on dietary welfare, health, and labor quality

  Warnings of deteriorating diet quality as income rises in China   Shift away from Chinese tradition diet   Higher consumption of animal foods and edible oils   Lower grain and vegetable consumption   Calories intake decreases   Increasing income hardly reduces vitamin A & D deficiencies

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Literature review   Strong focus on diet adequacy

  Levels of food and nutrient consumption as dependent variables   E.g. Berhman & Deolalikar (1987), Ravallion (1990), Skoufias (2002,

2009), Mangyo (2008)

  Studies on consumption quantity are insufficient to inform about how diet quality changes as income grows   Estimated income elasticity varies widely across studies   Consumption quantity reveals limited info about changes in diet structure

and quality

  Other aspects of diet quality are under-studied, despite being well-grounded in nutrition literature

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Research questions   Does diet quality necessarily deteriorate as income rises in

China?   Are there income effects and what form do they take?   Do income effects change over time?

  Are there education effects?

  Contribution:   Directly examine income effects on an essential aspect of diet quality

that no economists has paid attention to: diet variety   Most recent time period

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Data

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  China Health and Nutrition Survey 2004, 2006, 2009

  Multi-stage, randomized cluster sampling design

  9 provinces, approx. 3,800 households/year

  Pool sample: 20,307 adults (18-60 years old) from 4,506 households

Methodology

  Dependent variable:   Diet variety, measured by number of major food groups consumed

  Repeated cross-sectional regression models   OLS :

  Poisson quasi-maximum likelihood:

where

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Income effects

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OLS   Poisson    

Model   Variable   2004   2006   2009   2004   2006   2009  

1   Income   0.073***   0.016   0.0092         0.064***   0.016**   0.0094*  

2  Income   0.114***   0.088***   0.035***   0.114***   0.087***   0.036***  

Income  squared   -­‐0.0082*   -­‐0.0046***   -­‐0.0014***   -­‐0.0094***   -­‐0.0051***   -­‐0.0016***  

3  

QuinJle  2   0.0074   0.056**   -­‐0.038         0.014   0.076**   -­‐0.038  

QuinJle  3   -­‐0.034   0.015   -­‐0.043         -­‐0.024   0.039   -­‐0.041  

QuinJle  4   0.108***   0.117***   -­‐0.022         0.119***   0.137***   -­‐0.018  

QuinJle  5   0.138***   0.149***   0.101***   0.143***   0.159***   0.096***  

*  p  <  0.10,  **  p  <  0.05,  ***  p  <  0.01  

  Upward concave relationship between income and diet variety   Income effects vary across income groups   Income effects weaken over time

Income effects (cont’)

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  Marginal income effect is positive, stronger among low income groups

  Income effects weaken over time

0.00

0.02

0.04

0.06

0.08

0.10

0.12

Quintile 1 Quintile 2 Quintile 3 Quintile 4 Quintile 5

Marginal effects at mean income

2004 2006 2009

Education effects

  Higher education attainment, higher diet diversity   Difference in impacts of vocational training and university education are

not significant at 10% level

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OLS   Poisson    

Educa=on  level   2004   2006   2009   2004   2006   2009  

Primary   0.128***   0.032   0.042   0.133   0.036   0.049  

Secondary   0.154***   0.106***   0.088***   0.159***   0.107***   0.095***  

High  school   0.217***   0.161***   0.150***   0.217***   0.164***   0.158***  

VocaJonal  training   0.322***   0.340***   0.296***   0.306***   0.321***   0.287***  

University  &  above   0.338***   0.279***   0.376***   0.301***   0.243***   0.341***  

*  p  <  0.10,  **  p  <  0.05,  ***  p  <  0.01    Base  educaJon  category  is  “No  educaJon”    

Preliminary conclusion   Household income has positive impact on diet variety.

  Income effects are stronger among low income groups, but diminish over time.

  Education matters.

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Issues and Steps forward   Refine model specification and functional form

  Address issue of endogeneity between household income and diet variety

  Explore a diet quality index as a more comprehensive measure of diet quality

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Thank you

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Rationale for diet variety   Diet variety as dependent variable

  Unambiguous and well-grounded in nutrition literature   Widely recommended by government’s dietary guidelines   Incorporated in well-known diet quality indexes

  Construction of variety measure   Diet variety is most commonly measured by no. of food groups

consumed (Ruel 2005)   Food group classification is based Chinese Food Composition Table

(Yang et al. 2004, 2009), Chinese dietary guidelines 2007, and Diet quality index – International (Kim et al. 2003)

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Income effects

  Upward concave relationship between income and diet variety   Marginal income effect is smaller among high income groups

  Income effects weaken over time – flatter curves Note: The curves represent the predicted quadratic relationship between income and diet variety, while holding all other

regressors constant. Thus, values on the vertical axis do not represent nominal value of diet variety.

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- 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45

0 3 6 9 12 15 18

Pred

icte

d di

et v

arie

ty

Household income per capita (10,000 Yuan)

Predicted diet variety based on Model 2 and mean income of percentiles

2004 2006 2009

Income marginal effects

  Marginal income effect is smaller among high income groups   Need to refer to nutrition literature to assess the benefit of

having 1 additional food group in diet

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OLS   Poisson    

Income  Marginal  effect   2004   2006   2009   2004   2006   2009  

Sample  mean   0.099      0.078   0.031     0.097     0.076     0.031    

Mean  of  quinJle  1   0.112     0.086     0.034     0.111     0.086     0.035    

Mean  of  quinJle  2   0.108      0.084     0.033     0.107     0.083     0.034    

Mean  of  quinJle  3   0.104      0.081     0.032     0.102     0.080     0.032    

Mean  of  quinJle  4   0.097      0.077      0.030     0.094     0.075     0.030    

Mean  of  quinJle  5   0.076      0.061      0.024     0.070     0.058     0.023    

Compare Model 2 and Model 3

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0.00

0.05

0.10

0.15

0.20

0.25

Quintile 2 Quintile 3 Quintile 4 Quintile 5

Income effects, as compared to Quintile 1

2004 - model 2 2006 - model 2 2009 - model 2 2004 - model 3 2006 - model 3 2009 - model 3

Community-fixed effects OLS   Poisson    

Province   2004   2006   2009   2004   2006   2009  Heilongjiang   -­‐0.011   -­‐0.049   -­‐0.088**     -­‐0.0038   -­‐0.0392   -­‐0.076*  

Jiangsu   -­‐0.3889**   -­‐0.706***   -­‐0.797***   -­‐0.347***   -­‐0.617***   -­‐0.718***  

Shandong   -­‐0.289***   -­‐0.690***   -­‐0.487***   -­‐0.247***   -­‐0.641***   -­‐0.419***  

Henan   -­‐0.359***   -­‐0.642***   -­‐0.625***   -­‐0.316***   -­‐0.568***   -­‐0.564***  

Hubei   -­‐0.683***   -­‐0.917***   -­‐0.894***   -­‐0.670***   -­‐0.879***   -­‐0.849***  

Hunan   -­‐0.453***   -­‐0.800***   -­‐0.881***   -­‐0.434***   -­‐0.722***   -­‐0.829***  

Guangxi   -­‐0.838***   -­‐1.216***   -­‐1.175***   -­‐0.991***   -­‐1.369***   -­‐1.088***  

Guizhou   -­‐0.435***   -­‐0.6623***   -­‐0.600***   -­‐0.395***   -­‐0.587***   -­‐0.492***  

• p  <  0.10,  **  p  <  0.05,  ***  p  <  0.01  • Base  province  is  Liaoning  

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  Provincial factors play a significant role in determining diet variety

  Considerable differences across some provinces

Checking multicollinearity

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Model  2   2004   2006   2009  Age  squared   56.37   56.76   55.24  age   56.03   56.45   54.96  HH  income  pc   5.26   4.18   3.74  HH  income  pc  squared   4.53   3.83   3.53  EducaJon  level  -­‐  2   3.21   3.18   3.02  Province_43   2.46   2.74   2.7  EducaJon  level  -­‐  1   2.44   2.58   2.59  EducaJon  level  -­‐  3   2.43   2.51   2.26  Province_32   2.29   2.45   2.13  Province_42   2.25   2.44   2.11  Province_23   2.23   2.41   2.08  Province_37   2.06   2.28   1.92  Province_41   2.04   2.06   1.87  EducaJon  level  -­‐  4   1.84   2.03   1.85  Province_52   1.75   1.94   1.85  Price  -­‐  soy  oil  (log)   1.65   1.91   1.79  EducaJon  level  -­‐  5   1.64   1.88   1.76  Province_45   1.59   1.67   1.54  Price  -­‐  tofu  (log)   1.49   1.62   1.51  Price  -­‐  cabbage  (log)   1.35   1.55   1.42  Rural   1.33   1.41   1.38  Price  -­‐  rice  (log)   1.23   1.38   1.32  Price  -­‐  tofu  (log)   1.21   1.33   1.24  HH  size   1.2   1.27   1.23  Price  -­‐  pork  (log)   1.13   1.24   1.22  Gender   1.06   1.06   1.04  Mean  VIF   6.23   6.31   6.05  

Descriptive Statistics

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No.  of  food  groups  consumed   2004   2006   2009  

Mean   1.72   1.77   1.89  Median   2   2   2  Standard  deviaJon   0.77   0.80   0.83  Percentage  

0   0.24%   0.31%   0.10%  1   43.38%   41.76%   36.25%  2   43.30%   41.25%   42.18%  3   10.43%   13.85%   17.94%  4   2.36%   2.56%   3.15%  5   0.29%   0.28%   0.39%  

HH  income  pc  (Yuan),  adjusted  to  adult  equivalence  scale   2004   2006   2009  

Sample  mean                            9,111                                    10,828                                    14,951    

Mean  of  quinJle  1                            1,352                                    1,505                                    1,622    

Mean  of  quinJle  2                            3,899                                    4,123                                    6,481    

Mean  of  quinJle  3                            6,439                                    7,219                                    10,442    

Mean  of  quinJle  4                            10,455                                    11,649                                    16,682    

Mean  of  quinJle  5                            23,256                                    28,671                                    38,782    

Dietary guidelines for Chinese residents

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1.  Eat  a  variety  of  foods,  mainly  cereals  including  appropriate  amount  of  coarse  grains    

2.  Consume  plenty  of  vegetables,  fruits  and  tubers      

3.  Consume  milk,  soybean  or  dairy-­‐  or  soybean-­‐products  everyday  

4.  Consume  appropriate  amounts  of  fish,  poultry,  eggs  and  lean  meat  

5.  Use  less  cooking  oil;  choose  a  light  diet  which  is  also  low  in  salt  

6.  Do  not  over  eat,  exercise  every  day,  and  maintain  a  healthy  body  weight  

7.  RaJonally  distribute  the  daily  food  intake  among  the  three  meals,  correctly  choose  snacks  

8.  Drink  sufficient  amount  of  water  every  day,  raJonally  select  beverages    

9.  If  you  drink  alcoholic  beverages,  do  so  in  limited  amounts  

10.  Choose  fresh  and  sanitary  foods  

Source: Ke (2011)

Food classification

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Food  groups   Foods  sub-­‐groups  

Grain   Wheat,  rice,  corn,  barley,  millet,  tubers  

Vegetable   Root,  stem,  leafy,  and  flowering  vegetables  

Fruit   Fruits  

Meat   Pig,  cakle,  mukon,  poultry  ,  fish,  egg,  beans,  and  products  

Dairy   Milk  and  dairy  products  

Others  Fungi,  nuts  &  seeds,  infant  food,  ethnic  foods  &  cakes,  fast  foods,  beverages,  alcoholic  beverages,  sugars  &  preserves  &  honey,  fats  &  vegetable  oils,  condiments  

Source: Chinese Food Composition Tables (Yang et al. 2004, 2009)

Food classification

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Source: Ke (2011)