1. Chapter 6 From Demand to Welfare McGraw-Hill/Irwin Copyright © 2008 by The McGraw-Hill Companies, Inc. All Rights Reserved.

2. Main Topics Dissecting the effects of a price change Looking at Substitution and Income Effects Measuring changes in consumer welfare using demand curves Measuring changes in consumer welfare using cost-of-living indexes Labor supply and the demand for leisure 6-2

3. Dissecting the Effects of a Price Change When a price increases, two things happen: That good becomes more expensive relative to others; consumers shift their purchases away from the more expensive good Consumers’ purchasing power falls Economists have learned a lot about consumer demand and welfare from thinking about price changes this way 6-3

4. Dissecting the Effects of a Price Change As the price of a good changes, the consumer’s well-being varies An uncompensated price change is one with no change in income A compensated price change is a price change and an income change that together leave the consumer’s well-being unaffected (although it effects the consumer’s bundle choices). 6-4

5. Dissecting the Effects of a Price Change An example to help you understand…not exactly the same, but similar is…. The US govt. pays wages to its employees. As the US is a big place and costs of living vary between areas, the govt. has to maintain similar salaries (in terms of purchasing power) between employees no matter where they work. In some places, the costs and hence the pay is substantially more than in other places. 6-5

6. Effects of a Price Change In other words, in some places, the government has to pay additional money to leave their employees’ welfare unaffected by location. This is similar to a compensated price change. 6-6

7. Figure 6.1: Compensated Price Effects 6-7

8. Substitution and Income Effects Effect of a Compensated Price Change = Effect of an Uncompensated Price Change + Effect of Providing Compensation 6-8

9. Substitution and Income Effects Uncompensated price change has two parts: Substitution effect: the effect on consumption of a compensated price change, causing the consumer to substitute one good for another. Isolates the influence of the change in relative prices. Income effect: the effect on consumption of removing the compensation after creating a compensated price change, affecting the consumer’s purchasing power Isolates the influence of the change in purchasing power 6-9

10. Substitution and Income Effects Substitution effect involves: Movement along an indifference curve To a point where the slope is the same as the new budget line Income effect involves: Parallel shift in the budget constraint Toward the origin for a price increase Away from the origin for a price decrease 6-10

11. Figure 6.2: Substitution and Income Effects 6-11 Dark Gray = Uncompensated Price Effect Yellow=Income Effect Grey=Substitution Effect.

12. Direction of Substitution Effect Substitution effect of a price increase is: Negative for price increase Positive for price decrease Consumer substitutes away from the good that becomes relatively more expensive 6-12

13. Figure 6.3: Direction of the Substitution Effect for a Price Increase 6-13

14. Direction of Income Effect Direction of income effect depends on whether the good is normal or inferior Increase in the good’s price reduces the consumer’s purchasing power Consumer will buy less of the good if it is normal, but more if it is inferior Income effect of a price increase is: Negative for normal good Positive for inferior good 6-14

15. Figure 6.4: Direction of the Income Effect for a Price Increase 6-15 Erin buys meat and potatoes. Start at L1. Potatoes are$.5/lb. Beef is $3/lb. Income is $36/mon. Price of potatoes falls to $.25. Pivot to L2. Impl. Compensation. Subs. Effect: Move to bundle C…as potatoes are now relatively cheaper. Income Effect: No compen., move back to L2 and bundle B and buy less potatoes than with C.

16. Direction of Income and Substitution Effects Substitution effect is: Negative for a price increase Positive for a price reduction For a normal good, the income effect reinforces the substitution effect: Negative for a price increase Positive for a price reduction For an inferior good, the income effect opposes the substitution effect: Positive for a price increase Negative for a price reduction 6-16

17. Why Do Demand Curves Slope Downward? The Law of Demand states that demand curves slope downward Substitution effect is always consistent with Law of Demand For normal goods, income effect reinforces substitution effect Normal goods always obey the Law of Demand Theoretically, if income effect for an inferior good is large enough to offset substitution effect, this could violate Law of Demand 6-17

18. Figure 6.5: Giffen Good Giffen goods are inferior, and the amount purchased increases as the price rises Income effect is larger than the substitution effect 6-18

19. Giffen Goods Giffen goods are rare. Why? Most goods are normal. If spending on a good accounts for a small fraction of a consumer’s budget (as with most products), even a large increase in the good’s price doesn’t have much of an impact on the consumer’s overall purchasing power. So the impact of the income effect is small. 6-19

20. Giffen Goods Giffen good examples. Potatoes in the Irish Potato Famine. Shochu in Japan. Low grade alcohol If income goes up, people drink less and buy better quality sake. Therefore it is an inferior good. But as price of shochu rises, people appear to buy more and consume less sake. A study estimates that price elasticity for special grade sake is -6.11 and +8.81 for shochu. 6-20

21. Compensating Variation How can a consumer measure economics gains and losses in monetary terms? Compensating variation: the amount of money that exactly compensates the consumer for a change in circumstances Example: If the compensating variation for a gasoline tax is $50, then the consumer is better off with the tax as long as he receives a rebate for more than $50 Another….price of soup increases compensation is given to make the consumer as well off as before. 6-21

22. Consumer Surplus Consumer surplus is the net benefit a consume receives from participating in the market for some good Consumer’s demand curve measures the gross benefit of consuming a good Consumer surplus is the area below the demand curve and above a horizontal line at the price Amount of money that would compensate the consumer for losing access to the market, compensating variation 6-22

23. Figure 6.6: Consumer Surplus 6-23 Remember…the formula for finding the area of a triangle, ie. (b) is Height X Width X ½…. The formula for a square or rectangle is…?

24. Using Consumer Surplus to Measure Changes in Welfare Some public policies alter prices and amounts of traded goods Consumer surplus is useful, allows us to measure change in net economic benefit from the policy This is another way to describe compensating variation for the policy Example: Policy reduces consumer surplus from $100 to $80 Must provide her with $20 (cash or value) to if the govt. wishes to compensate fully for the policy’s effects 6-24

25. Figure 6.7: Change in Consumer Surplus When price = $2, consumer surplus is grey and brown shaded areas When price = $4, consumer surplus is grey area Brown area is change in consumer surplus 6-25

26. Consumer Surplus Example Abigail’s monthly demand curve for cell phone service is W=300-200P W. W=# of minutes and P W is price/minute of service. Say that P W =$.50. Calculate her consumer surplus. Find Intercepts, draw curve, calc. surplus What is P W increased to $1.00. What is the change in Abigail’s consumer surplus? 6-26

27. Consumer Surplus Example If Abigail’s demand curve for minutes of wireless telephone service is W = 300 – 200PW, then her demand curve intersects the price axis at a price of $1.50. (This is the lowest price at which she would demand exactly zero minutes of wireless telephone service; it can be found by plugging 0 in for W.) If the price is $1, this means that the height of the triangle that shows her consumer surplus is $0.50. To figure out the width of the triangle, we only need to know how many wireless minutes Abigail demands at the new price of $1.00, which is just W = 300 – 200(1.00), or 100. So the area of this triangle is ½($0.50)(100) = $25. This represents a decrease in consumer surplus for Abigail of $75, since we know from Worked-Out Problem 6.3 that her original consumer surplus (at a price of $0.50) was $100 6-27

28. Measuring Changes in Consumer Welfare Using Cost-of-Living Indexes A cost-of-living index measures the relative cost of achieving a fixed standard of living in different situations Commonly used to measure changes in the cost of living over time Can be used to measure changes in consumer well-being due to public policies that alter prices or income Example: Consumer Price Index…think of the one we saw earlier in this chapter’s slides. 6-28

29. Cost-of-Living Indexes: Basics Base value of one during some specific period Level of index in the base period is unimportant All that matters is percentage change in the index Example: Value of index in 1998 is 1; value in 2006 is 1.2, then cost of living has risen by 20% Ideally should allow us to quickly evaluate changes in consumer well-being following changes in prices and income 6-29

30. Cost-of-Living Indexes: Basics Price indexes are often used to calculate real income levels from nominal ones. Nominal income is the amount of money actually received in a particular period. Real income is the amount of money received in a particular period adjusted for changes in purchasing power that alter the cost of living over time. 6-30

31. Cost-of-Living Indexes: Basics Use to convert nominal income into real income If real income has risen, then: Nominal income has grown more rapidly than then cost of living Consumer should be better off Or if real income is static then changes in prices have been mirrored by changes in income. Ideally, change in real income should measure the change in the consumer’s well-being Difficult to construct a good cost-of-living index because different prices change by different proportions, ie. Cost of housing vs. cost of gasoline. 6-31

32. Fixed-Weight Price Indexes Select a consumption bundle and measure its cost in multiple time periods, using prices at which the goods were available Fixed-weight price index: measures percentage change in the cost of a fixed consumption bundle Easy to calculate, requires no information about consumer preferences But what consumption bundle is appropriate? Example: Laspeyres price index which takes the bundle purchased in the base period and used in subsequent periods. But is this approach the best one? Are there problems? 6-32

33. Fixed-Weight Price Indexes Laspeyres price index which takes the bundle purchased in the base period and used in subsequent periods. But is this approach the best one? Are there problems? One issue is the substitution bias. Fails to capture the consumer’s tendency to moderate the impact of a price increase by substituting away from goods that have become more expensive. Therefore, the index overstates the cost of living. 6-33

34. Labor Supply Consumer buy goods and services Many are also sellers (e.g., sell their work effort) Labor supply refers to the sale of a consumer’s time and effort to an employer To study labor supply, economists often study demand for leisure 6-34

35. Labor-Leisure Choice: An Example Javier’s possible income sources: Allowance of $30 per day (no strings attached!) Job that pays $5 per hour 14 hours per day available to allocate toward work and/or leisure Assume all money spent on food Decision about how many hours of leisure to enjoy (and thus how many to work) depends on his preferences 6-35

36. Figure 6.10: Labor-Leisure Choice With the dark red preferences, Javier chooses 8 hours of leisure (6 hours of work) per day With the light red preferences, Javier chooses not to work 6-36

37. Effect of Wages on Hours of Work How does a change in wage affect a consumer’s budget line? In Javier’s case, he will have $30 to spend on food regardless of his wage Wage change rotates his budget line, getting steeper with higher hourly wages Points of tangency between indifference curves and budget lines form a price-consumption path This leads to Javier’s leisure demand curve in Figure 6.11(b) 6-37

38. Figure 6.11: Leisure Demand and Labor Supply Curves 6-38

39. Labor Demand Curves Do labor demand curves obey the Law of Demand? Some people may have backward bending labor supply curves Increase in wage reduces the supply of labor for some range of wages Due to income effects: People own more time than they consume Increase in wage rate raises their purchasing power Increases their consumption of leisure, a normal good 6-39

40. Figure 6.12: Effects of Increase in Wage Rate Increase in wage rate leads to opposing income and substitution effects Income effect overwhelms substitution effect Wage increase results in reduced number of labor hours 6-40

41. Effect of Wages on Labor Force Participation Given that backward bending labor supply curves exist: Can a wage reduction cause someone who would not otherwise work to enter the labor market? NO! Can a wage increase drive someone who would otherwise work out of the labor market? NO! 6-41

42. Figure 6.13: Effect of Wage Rate on Labor Force Participation A wage lower than the wage represented on the black budget line cannot lead Javier to enter the labor force A wage increase rotates the budget line upward and can entice him to choose to work (e.g., by selecting bundle G) 6-42

43. Other Demand Curves Uncompensated demand curves, AKA Marshallian demand curves always slope downward. Compensated demand curves, AKA Hicksian demand curves, correspond to different levels of the consumer’s well-being. 6-43

44. Other Demand Curves Normal good – uncompensated demand curve is flatter. (Income & Subs. Effects work in the same direction so price change would produce a larger change in the uncompensated demand.) Inferior – compensated demand curve is flatter. (Income and subs. Effects work in opposite directions.) 6-44

45. Review Problems Sam currently earns $30,000/year. The govt. is considering a policy that would increase Sam’s income by 12%, but raise all prices by 8%. What is Sam’s compensating variation for the proposed policy? Can you compute it without knowing his preferences? Why/not? 6-45

46. Review Problems If Sam is a utility maximizer, then he is spending all $30,000 of his income on goods that make him happy. If the government increased his income by 12%, it would increase to $33,600. If the prices increased by 8%, then his current consumption bundle would increase in cost to $32,400. At his previous level of consumption, Sam now has $1,200 leftover to spend on more goods and services. We could take this $1,200 from him and he would remain just as happy as he was before. Therefore, the compensating variation for this income and price change is –$1,200. 6-46

47. Review Problems Is it possible for the true cost of living to rise for one consumer and fall for another in response to the same change in process? Explain. If yes, how…give an example with a graph. If no, why not? 6-47

48. Review Problems It is possible because people have different preferences. In the drawing to the right, a decrease in the price of X and an increase in the price of Y affect consumer A and consumer B differently. Consumer A, who prefers good X, is better off (on a higher indifference curve), and consumer B, who prefers good Y, is worse off (on a lower indifference curve). 6-48