welcome to day 10
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Welcome to Day 10. Principles of Microeconomics. Price elasticity is the ratio of the percent change in quantity demanded to the percent change in price. Elasticity of demand = percent change in quantity demanded divided by percent change in price. Ed = % Qd % P. - PowerPoint PPT PresentationTRANSCRIPT
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Welcome to Day 10
Principles of Microeconomics
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Price elasticity is the ratio of the percent change in quantity demanded to the percent change in price.
Elasticity of demand = percent change in quantity demanded divided by percent change in price.
Ed = %Qd % P
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So a t-shirt shop notices that when they raise their price by 5%, they
lose 10% of their customers. What is their elasticity of demand?
-10% = -25%
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What does the -2 mean?
For every 1 percent they raise their price, their sales drop by 2%.
The elasticity of demand number always means that for every 1% they raise their price, their sales
drop by X%
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Another store checks their data and sees when they raise their
price by 10%, they lose 5% of their sales. What is their elasticity of
demand?
-5% = -0.510%
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For every 1% they raise their price, they lose 0.5% of their sales.
What if the stores lowered their price? Then a store with an elasticity of -2 should gain 2% in sales for every 1%
drop in price. A store with an elasticity of -0.5 should gain 0.5% more sales with every 1 percent drop in price.
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Unfortunately, the data does not usually come in percentage terms. Usually you know the starting and ending prices, and the starting and
ending quantities, and have to convert these to percentages.
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Here’s how to do that.
%Qd = (Q2-Q1)/[(Q1+Q2)/2]
%P = (P2-P1)/[(P1+P2)/2]
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So the elasticity formula in all its glory is
Ed = (Q2-Q1)/[(Q1+Q2)/2] (P2-P1)/[(P1+P2)/2]
The textbook writes it this way
PPQQeD /
/
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Notice that we are calculating percentage changes in an unusual way. Usually, you
would just divide the change by the starting value, not the average of the
starting and ending value.
By doing it this way, we get the same elasticity answer if the price goes up from
$10 to $12 or down from $12 to $10.
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The own price elasticity number will always be negative by the
math, but it is common to drop the negative sign and write it as its
absolute value. So -2 becomes 2.
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What is the range of possible own price elasticities?
0
81
Ed < 1 then Inelastic Demand
Ed > 1 then Elastic Demand
Ed = 1 then Unit Elastic Demand
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Total Revenue for a store isTR = P x Q
Imagine a store with a very inelastic demand, say 0.3 If they raise their price 10%, their sales
drop by 3%. Does their revenue go up or down?
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TR ? = P 10% x Q 3%
TR goes up.
Whenever the elasticity is below 1, the percent drop in purchases is
always less than the percent rise in price and revenue always rises when
price rises.
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What if the elasticity is greater than one? Then the percentage drop in sales is
always greater than the percent rise in price and the revenue always fall.
TR ? = P 3% x Q 10%
TR goes down.
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Inelastic DemandRaise price revenue goes up.
Lower price revenue goes down.
Elastic Demand Raise price revenue goes down.Lower price revenue goes up.
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And if the demand is unit elastic?Then the percentage change in price
equals the percentage change in sales, and revenue remains unchanged.
Unit Elastic Demand (Ed = 1) Raise price revenue stays the same.Lower price revenue stays the same.
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What happens if zero customers stop buying when the price rises?
Ed = %Qd % P
Ed = 0.This is called perfectly inelastic demand.
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Note that an Ed = 0 does not mean the store has 0 customers, it
means it loses 0 customers then it raises its price.
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And what if the store loses every customer when it raises its price the
tiniest possible amount?
As %P goes to 0, %Qd stays constant. This fraction is going to infinity.
Ed = %Qd % P
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Perfectly Inelastic Demand Curve
Perfectly Elastic Demand Curve
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Welcome to Day 11
Principles of Microeconomics
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What determines if the elasticity is high or low?
1) Number and closeness of substitutes.
2) Percentage of budget spent on the good.3) Time.
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1) Number and closeness of substitutes.
The more and better substitutes available for a good, the more
consumers buy these substitutes in place of the good when the price
of the good rises.
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Good substitutes high elasticityPoor substitutes low elasticity
Tell me some high and low elasticity items.
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2) The percentage of your budget spent on the good.
When the price of the car you are thinking of buying doubles, you are more likely to
back off buying it than when the price of a candy bar doubles.
The greater the percentage of your budget spent on the good, the higher its elasticity
of demand.
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3) Time
The more time you have to respond, the higher the elasticity
of demand.
What can you do if the price of gas rises?
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The textbook tells us that the short-run elasticity of demand for oil in the United States is .06, but
the long-run elasticity is .45
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Reviewing the 3 factors that determine elasticity of demand.
1) Number and closeness of substitutes.
2) Percentage of budget spent on the good.3) Time.
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Income elasticity of demand is the percentage change in quantity demanded at a specific price divided by the percentage change in income that produced the demand change, all other things unchanged. Ei = %D D = Demand % I I = Income
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What does the income elasticity number tell you?
It is the percent change in purchases if there is a 1 percent rise in income. For example, an
answer of 0.7 means for every 1% rise in income, people buy 0.7
percent more of the good.
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When the income elasticity is positive, that means people buy more of the good when their income goes up or
less when their income goes down. In other words, a normal good.
When the income elasticity is negative, people buy less when their income goes up, in other words, an
inferior good.
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Cross price elasticity of demand is the percentage change in the quantity
demanded of one good or service at a specific price divided by the
percentage change in the price of a related good or service.
EX,Y = %Dx % Py
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Remember how to find the percentage change in X.
It is the change in X divided by the average of the starting and ending quantities of X. And don’t forget to
check for the sign.
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Cross-price elasticity is positive when the two goods are
substitutes.
It is negative when the two goods are complements.
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Price elasticity of supply is the ratio of the percentage change in
quantity supplied of a good or service to the percentage change
in its price, all other things unchanged.
pricein change %
suppliedquantity in change %se
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The terminology from the elasticity of demand transfers over to the
elasticity of supply.
Es > 1 is Elastic SupplyEs < 1 is Inelastic Supply
Es = 0 is Perfectly Inelastic SupplyEs = Infinity is Perfectly Elastic Supply.
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Supply Curves and Their Price Elasticities
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The more time suppliers have to build more factories, the greater the increase in the amount of the good will be in response to a given
higher price.
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P1
P2
Which supply curve has the larger elasticity?
Q Cars
S1
S2
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Elasticity and the War on Drugs
How can we spend so much money and manpower and drugs still be so
readily available?
http://www.drugsense.org/cms/wodclock
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How do we represent the war on drugs in a supply and demand diagram?
Is the elasticity of demand for most illegal drugs going to be high or low?
Does cocaine have good substitutes or few substitutes?
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D1 is low elasticity. D2 is high elasticity.
0 50000 100000 150000 200000 250000 300000$0.00
$10.00
$20.00
$30.00
$40.00
$50.00
$60.00
$70.00
P2
P1 D2
D1
Q1Q2AQ2B
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How much cocaine has been destroyed? What is the drop in usage?
0 50000 100000 150000 200000 250000 300000$0.00
$10.00
$20.00
$30.00
$40.00
$50.00
$60.00
$70.00
P2
P1
S2
S1
D
Q1Q2
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Q1 to Q2 is the drop in usage = 25,000Amount destroyed = 125,000
0 50000 100000 150000 200000 250000 300000$0.00
$10.00
$20.00
$30.00
$40.00
$50.00
$60.00
$70.00
P2
P1
S2
S1
Amt. De-stroyed
D
Q1Q2
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So what has happened? Used to be 150,000 made and bought for 20 bucks. Now 250,000 is made, half is destroyed, and 125,000 is
bought for $40.
The main effect of destroying drugs in this model is that more is made.
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What is the elasticity of cocaine in this model? Q1-Q2/[(Q1+Q2)/2] divided by P2-P1/[(P1+P2)/2] is
(25,000/ 137,500)/(20/30)= .18/.67 = .2
What if the elasticity is high?
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Q1 to Q2 is the drop in usage = 60,000Amount destroyed = 90,000
0 100000 200000 300000$0.00
$10.00
$20.00
$30.00
$40.00
$50.00
$60.00
P2
P1
S2
S1Amt. De-stroyed
D
Q1Q2
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What is the elasticity of cocaine now?
Q1-Q2/[(Q1+Q2)/2] divided by P2-P1/[(P1+P2)/2] is
(60,000/120,000)/(6/23)= .5/.26 = 1.92
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Notice how much more the price rises when the elasticity is low.
What are some side effects of cocaine prices going high?
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Now let’s look at the effect of government subsidized student
loans.
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Students are given $300,000,000 to go to college (doubling current tuition spending)
0 50000 100000 150000 200000 250000$0.00
$1,000.00
$2,000.00
$3,000.00
$4,000.00
$5,000.00
$6,000.00
$7,000.00
$8,000.00
$9,000.00
D2
S
D1
Tuition
Number Students
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Number of students rises from 100,000 to 130,000. Tuition rises
from $3,000 to $5,600.
Everyone gets to pay the higher tuition, not just the additional
students.
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And don’t forget, these are loans, so you still have to pay the money
back.
So who is helped more by government guaranteed loans?
The students … or the colleges and banks?
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And this result is because of elasticity of supply. What if elasticity of supply is high?
0 50000 100000 150000 200000 250000$0.00
$1,000.00
$2,000.00
$3,000.00
$4,000.00
$5,000.00
$6,000.00
$7,000.00
$8,000.00
D1
D2
S
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Welcome to Day 12
Principles of Microeconomics
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Our goal is to answer the 3 fundamental questions well.
1) What to produce?What people want.2) How to make it?Produce efficiently.
3) Who gets what is produced?People who value it.
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An economy that does these things is operating efficiently.
Efficient
The allocation of resources when the net benefits of all economic
activities are maximized.
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An economy that is operating efficiently has both:
1) Efficient production2) Efficient allocation of goods.
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Will a market economy do these things?
How does a business make money?Producing a lot of what people
want the most and selling it.
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The better a business correctly estimates what its customers
value, and makes a lot of those things, the higher its profit.
And of course, we want the economy to be able to adjust to changing circumstances. Will a
market economy do that?
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Rainy Winter Increases Demand
0 50000 100000 150000 200000 250000 300000$0.00
$2.00
$4.00
$6.00
$8.00
$10.00
$12.00
$14.00
$16.00
D1
SP
Q
P1 D2
P2
Q1 Q2
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Can a command economy do this?
The incentive problem and the information problem.
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The Incentive Problem
What does an umbrella businessman get if he gets umbrellas quickly out to a
rainy area?
What does the 2nd undersecretary of umbrellas in Washington get if he gets umbrellas quickly out to a rainy area?
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The Information Problem
How does the 2nd Undersecretary of Umbrellas know we need more
umbrellas in Bakersfield?
How do private business owners of umbrella companies know?
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Every time you go shopping, it is a transfer of information fest!!!
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You are letting sellers know what you want.
Sellers are letting you know what they can make at what
cost.
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The Invisible Hand
Adam Smith – 1776The Wealth of Nations
Because trades are voluntary, in helping yourself, when you are
helping yourself, you help others also.
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The way for the businessman to make money is to most effectively
serve his customers.
In doing what is best for him, he is being lead, as if by an “invisible
hand” to help society.
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So what can go wrong?
Market Failure - The failure of private decisions in the
marketplace to achieve an efficient allocation of scarce resources.
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In other words, we are making too much or too little of something
because of a failure to properly take account of its benefits and costs.
What markets does the government heavily regulate in the U.S.
economy?
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Externalities – an action taken by a person or firm that imposes
benefits or costs outside of any market exchange.
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We’ve seen these pictures earlier this semester, but we didn’t have a name for what they were yet. Now
we do.
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So what to do?
We have seen one solution, which is government regulation of the industry.
There is another, which is to charge, or tax, people for the harm they are doing
to others. This will “internalize the externality.
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Here is our factory causing $100,000 worth of harm to the people around the factory. It could cut the pollution in half by spending $25,000 on scrubbers. Will the owner do it?What if he had to pay $1 in taxes for each $1 harm done by his pollution?
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Some people have proposed a “carbon tax” as part of the solution
to global warming.
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Welcome to Day 13
Principles of Microeconomics
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Besides externalities, there is another type of marked failure is
known as public goods.
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Public Goods
A good for which the cost of exclusion is prohibitive and for which the marginal cost of an
additional user is zero.
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For example, a streetlight placed on a block.
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Examples of Public Goods1) Streetlights
2) Roads3) National Defense
4) Light Houses5) Free Television
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The Free Rider Problem
Free Riders – People or firms that consume a public good without
paying for it.
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The government gets around the problem by not asking you to pay,
but telling you to pay.
![Page 84: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/84.jpg)
In theory, the government can handle this problem. In practice, we still have our old problems of:
1) information.2) incentive.
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Tragedy of the Commons - What happens when property rights are
not assigned?
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Once property rights are assigned, problem solved. This is why the cow population is thriving and whales are hunted almost to
extinction.
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The air is a commons.
Unless the government enforces regulation or taxes.
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Of course, we have talked about air pollution before, under
externalities.
The tragedy of the commons isn’t really a new thing, it is a subset of
externalities.
Who owns the air?
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Welcome to Day 14
Principles of Microeconomics
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Two Time Frames
Short-Run: Some inputs are fixed
Long-Run: All inputs are variable
![Page 96: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/96.jpg)
Marginal Product of Labor (MPL) is the increase in total output gained
by adding one more worker.
Q/L
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N Q MPL0 0
201 20
302 50
253 75
104 85
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N Q MPL0 0
201 20
302 50
253 75
104 85
Why would MPL be rising?
![Page 99: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/99.jpg)
Specialization of Labor
1) Take advantage of natural abilities.
2) More practice and training at specific jobs.
3) Less time lost walking between jobs.
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N Q MPL0 0
201 20
302 50
253 75
104 85
Specialization of Labor Region
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N Q MPL0 0
201 20
302 50
253 75
104 85
Specialization of Labor Region
Why would MPL be falling?
![Page 102: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/102.jpg)
Diminishing Returns
As more variable factors are added to work with a fixed factor, eventually output rises at a
diminishing rate.
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N Q MPL0 0
201 20
302 50
253 75
104 85
Specialization of Labor Region
Diminishing Marginal Returns Region
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Productivity of Labor Measured in MPL
0 0.5 1 1.5 2 2.5 3 3.5 4 4.50
5
10
15
20
25
30
35
Number of Workers
Bush
els o
f Whe
at
Spec. of Labor Reg.
Dim. Mar. Ret. Reg.
![Page 105: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/105.jpg)
Average Product of Labor (APL) = Q/N
![Page 106: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/106.jpg)
Average-Marginal Rule:
When the marginal is above the average, the average rises; when the marginal is below the
averge, the average fall.
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N Q MPL APL0 0 0
201 20 20
302 50 25
253 75 25
104 85 21.25
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Marginal and Average Product of Labor on the same graph.
0 0.5 1 1.5 2 2.5 3 3.5 4 4.50
5
10
15
20
25
30
35
Number of Workers
Bush
els o
f Whe
at
APL
MPL
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Marginal and Average Product of Labor on the same graph.
0 0.5 1 1.5 2 2.5 3 3.5 4 4.50
5
10
15
20
25
30
35
Number of Workers
Bush
els o
f Whe
at
APL
S.o.L. Region D.M.R. Region
MPL
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Output
MPL
APL
Number Workers
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Fixed Costs (don’t change as production varies): Lease PaymentsInterest on LoansSome Insurance
Variable Costs (do change as production varies):LaborSupplyElectricity
![Page 112: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/112.jpg)
Q TFC TVC TC MC ATC0 100 0 100 -- - -1 100 20 120 20 1202 100 35 135 15 67.53 100 60 160 25 53.34 100 100 200 40 505 100 160 260 60 52
![Page 113: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/113.jpg)
If workers cost $10 each, how many workers did the firm hire
to build 1 radio?
How about 2 radios?
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Why does it take 2 full workers to make the first radio, but only another
1.5 to make the second radio?
The workers must be getting more productive. Why would that be?
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Why does it take 2 full workers to make the first radio, but only another
1.5 to make the second radio?
The workers must be getting more productive. Why would that be?
Specialization of Labor
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Why does it take 4 workers to make radio 4, but 6 workers to
make radio 5?
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Why does it take 4 workers to make radio 4, but 6 workers to
make radio 5?
Diminishing Marginal Returns
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Q TFC TVC TC MC ATC0 100 0 100 -- - -1 100 20 120 20 1202 100 35 135 15 67.53 100 60 160 25 53.34 100 100 200 40 505 100 160 260 60 52Above the green line is SoL. Below is DMR.
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Marginal Cost and Average Total Cost on the same graph.
0 1 2 3 4 5 6 70
20
40
60
80
100
120
140
Output
Cost
in D
olla
rs
ATC
MC
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Marginal Cost and Average Total Cost on the same graph.
MC
ATC
Output
Dollars
Fixed Cost
Specialization of labor
Diminishing Marginal Returns
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Welcome to Day 15
Principles of Microeconomics
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In the short-run, the size of the factory is fixed.
In the long-run, the size of the factory can be varied.
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The LRATC is made up of segments of the various possible SRATC curves.
![Page 124: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/124.jpg)
Economies of Scale - LRATC is falling as you produce more in a larger factory.
Constant returns to Scale - LRATC is staying the same as you produce more
in a larger factory.
Diseconomies of Scale - LRATC is rising as you produce more in a larger factory
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Why Economies of Scale?
1) Specialization of Labor
2) Mass Production
Techniques – Assembly Lines
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Why Diseconomies of Scale?
1) Command and Contr Control
Problems
2) Law of Increasing Opportunity Cost
Problems
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Would you always want to produce in constant returns to scale since
that is the lowest cost of production area?
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Would you always want to produce in constant returns to scale since
that is the lowest cost of production area?
No! How many customers you have and how much they are willing to pay matters also.
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Welcome to Day 16
Principles of Microeconomics
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Businesses operate in different environments, called market
structures.
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There are 4 market structures. Each market structure is defined
by:1) How many firms sell in it.
2) How close the firms products are to each other.
3) How easy it is to get into or out of the market.
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The first market structure is “Perfect Competition”
1) Many sellers and buyers.2) Firms sell identical goods.3) There is easy entry/exit.
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Because there are many firms selling identical products, the sales
price is the same for all firms.
These firms are called Price Takers.
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Perfect Competition examples are:
1) Small farms.2) Stockbrokers selling identical
stock.3) Miners.
4) Fishermen
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A small wheat farmer has a demand curve that looks like this:
Demand Curve
$5.98
P
Q
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He’s not worried that he will produce so much wheat he will drive the world price of wheat
down.
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The world demand curve for wheat is still downward sloping, but he is too small to make any difference.
Just like you buying potato chips.
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Marginal Revenue is the increase in total revenue gained with each
additional sale.
It is a before cost is taken out number.
For firms in perfect competition, marginal revenue = price.
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A small wheat farmer has a marginal revenue curve that looks
like this:
Demand Curve
$5.98
Marginal = Revenue Curve
Q
P
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The farmer does not get to pick his price, but he does get to pick his quantity of wheat grown. He will
do what makes him the most money.
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Q TR TC π Price=$100 0 2 -2 TR = P x Q1 10 10 0 π = Profit2 20 16 4 TR = Total 3 30 25 5 Revenue4 40 37 3 TC = Total
Cost
![Page 143: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/143.jpg)
Q TR TC π MR MC 0 0 2 -2 -- --1 10 10 0 10 8 2 20 16 4 10 63 30 25 5 10 9 4 40 37 3 10 12
![Page 144: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/144.jpg)
To maximize profit, produce the wheat that has MR>MC and don’t
produce the wheat that has MC>MR.
![Page 145: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/145.jpg)
If you can produce fractions rather than just integers, then produce
the level of output where MR=MC.
This is what the textbook calls the marginal decision rule.
![Page 146: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/146.jpg)
Just because you follow the marginal decision rule doesn’t mean you necessarily make a
positive profit. Sometimes the best you can do is to lose the least.
![Page 147: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/147.jpg)
Q TR TC π MR MC 0 0 20 -20 -- --1 10 28 -18 10 8 2 20 34 -14 10 63 30 43 -13 10 9 4 40 55 -15 10 12
What should you do here?
![Page 148: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/148.jpg)
Note that you can’t avoid a loss by shutting down. If you shut down,
you lose fixed cost.
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Is there a way to know if you are making a profit or losing money
just using the price and the ATC of production?
TR = P x QTC = ATC x Q
![Page 150: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/150.jpg)
TR = P x QTC = ATC x Q
The Q’s will be the same for both equations. So if P>ATC, this firm is making money. If P<ATC, this firm
is losing money.
![Page 151: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/151.jpg)
So how do you graph this all out?
First, the marginal decision rule: produce the quantity where
MR = MC
![Page 152: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/152.jpg)
Produce at Qπ to maximize profit.
0 0.5 1 1.5 2 2.5 3 3.5 4 4.50
2
4
6
8
10
12
14
Output
Cost
in D
olla
rs
MR
Qπ
MC
![Page 153: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/153.jpg)
MR
MC
Q
P
Qπ
Pπ
Here, MC intersects MR twice. Always use the 2nd point of interception.
![Page 154: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/154.jpg)
MR, MC, and P are not enough to know if you are making a positive profit. As fixed costs rise, these
numbers do not change, yet your profit is falling. You need to add
ATC.
![Page 155: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/155.jpg)
MR
MC
Q
P
Qπ
Pπ
Here we have profit because P>ATC.
ATC
![Page 156: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/156.jpg)
MR
MC
Q
P
Qπ
Pπ
Here we have a loss because ATC>P.
ATC
![Page 157: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/157.jpg)
When should a firm just give up and shut-down?
When its loss from operating is greater than its fixed cost.
![Page 158: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/158.jpg)
Firm 1 Firm 2TR $400 $400TFC $100 $100TVC $395 $405TC $495 $505Profit $-95 $-105
What should each firm do?
![Page 159: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/159.jpg)
Keep operating when TR>TVC.
TR = P x QTVC = AVC xQ
Keep operating when P>AVCShutdown when P<AVC
P = AVC is the shutdown price.
![Page 160: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/160.jpg)
Welcome to Day 17
Principles of Microeconomics
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MR
MC
Q
P
P1
How much will this firm produce at P1?
![Page 162: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/162.jpg)
MR
MC
Q
P
Q1
P1
What about at P2 and P3?
P2
P3
![Page 163: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/163.jpg)
MR1
MC
Q
P
Q1
P1
We have marked 3 points on the firms supply curve.
P2
P3
MR2
MR3
Q2Q3
![Page 164: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/164.jpg)
Supply Curve
Q
P
Q1
P1
The firm’s marginal cost curve is its supply curve down to the Shutdown Price (PS)
P2
P3=PS
Q2Q3
![Page 165: Welcome to Day 10](https://reader036.vdocuments.us/reader036/viewer/2022062501/5681689f550346895ddf3300/html5/thumbnails/165.jpg)
The market supply curve is all the individual supply curves added together.
Individual firm supply curves
Market Supply Curve
P
Q
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Now we add the demand curve and we get where the market price comes from
SP
Q
D
PE
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The market price for wheat is the price such that each farm, in response
to that price, wants to grow an amount of wheat which, when all the farms are added together, equals the
amount of wheat that customers want to buy at that price.
This is what chapter 3 said, also.
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Now let’s talk about the long-run, so enough time goes by that new
farms can enter the market.
Before we do so, let’s be a bit more exact about what we mean by cost
and profit.
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Explicit Cost is actual money paid out.
Implicit Cost is the value of resources used for which no
money is paid. For example: time and already owned land.
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Accounting profit is Total Revenue minus Explicit Cost.
Economic Profit is Total Revenue minus both Explicit and Implicit
Cost.
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The economic profit of a choice can also be understood as how much more you make doing this choice
than the next best choice.
You are offered $100 to work all day on project A and $60 to work all day on project B. What is your economic profit of choosing A?
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Suppose woman A and woman B want to start two similar businesses.
Woman A has an $80,000 job she would have to quit to run her
business, but woman B is unemployed and we count her time
as having 0 value. How does this affect their accounting and
economic profits?
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Woman A Woman BTotal Revenue $100,000 $100,000Explicit Cost $60,000 $60,000Accounting Profit $40,000 $40,000Implicit Cost $80,000 $0Economic Profit -$40,000 $40,000
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Economic profit is a better predictor of behavior. We would
predict woman A will not start this business and woman B will.
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So now enough time goes by for new wheat farms to open up.
When will new farms be started?
When wheat farms are making money, that is, have a positive
economic profit.
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How long will the new farms keep coming in? Remember, entry is
easy.
Till profits go to zero.
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If profits are negative (in other words, losses), then farms will
leave in the long-run until profits are zero.
So no matter where you start, profits in the long-run go to zero
because of easy entry/exit.
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So what does the long-run equilibrium look like? Let’s think
about how the long-run responds to an increase in demand.
Start at a long-run equilibrium with profits for the typical wheat farm at
$0.
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MR=P
MC
Q
P
P1
How much will this firm produce at P1?
ATC
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Now there is an increase in market demand and the price rises to P2 in the short-run.
Sshort-runP
Q
D1P1
D2
P2
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MR1=P1
MC
Q
P
P1
This firm is now making a profit. This attracts entry.
ATC
MR2=P2P2
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MR1=P1
MC
Q
P
P1
How far will the price have to fall until profit is back to zero?
ATC
MR2=P2P2
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There has to be a new equilibrium back at P1. For this to happen, the long-run supply
curve has to be flat.
Sshort-runP
Q
D1P1=P3
D2
P2
SLong-run
Q1 Q2 Q3
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MR1=P1
MC
Q
P
P1=P3
And profits are back to zero. BTW, this farm is back to producing where it started, so where is all the additional wheat coming from?
ATC
MR2=P2P2
MR3=P3
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But I fear we have provent too much. It looks like in the long-run, price always goes back to where it started, and I don’t believe this.
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MR1=P1
MC
Q
P
P1
How can we get back to zero profits as new firms come in with the price ending up higher than P1?
ATC
MR2=P2P2
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So now P3 will be higher than P1 when ATC rises as new firms enter.
Sshort-runP
Q
D1P1
D2
P2SLong-run
Q1 Q2 Q3
P3
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This case of rising ATC as new firms enter is called an “Increasing Cost
Industry”.
The first case where ATC stayed constant is called a “Constant Cost
Industry”.
Which case seems more likely?
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Could it even be possible that as more firms enter the market, the
ATC falls?
Think about what happens if wheat farms need tractors, and tractors
are made with economies of scale.
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For this “Decreasing Cost Industry”, the long-run price P3 will be lower than the starting price P1 if there is
an increase in demand. This means there must be a downward
sloping long-run supply curve.
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Now P3 is less than P1. And increase in demand has lead to a lower price.
Sshort-runP
QD1
P1
D2
P2
SLong-run
Q1 Q2 Q3
P3
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Let’s review and simplify. Increasing Cost Industry.
LRS slopes up.P
Q
D1P1
D2
SLong-run
Q1 Q2
P2
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Constant Cost Industry.LRS slopes straight across.
P
Q
D1
P1=P2D2
SLong-run
Q1 Q2
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Decreasing Cost IndustryLRS slopes down.
P
Q
D1
P1
D2
SLong-run
Q1 Q2
P2
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Where does all this leave the law of supply?
It is still true that short-run supply curves always slope up. But now
this is primarily because of diminishing marginal returns rather than the next worker getting worse.
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In the long-run, supply curves usually slope up as more resources are used and the workers get worse; but it is
possible for the supply curve to slope down if significant inputs are made with economies of scale. As we add more complexity to the model, our
previously simple answers grow more complex.
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Welcome to Day 18
Principles of Microeconomics
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Test Prep
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Welcome to Day 19
Principles of Microeconomics
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Test Day