1. 1 Chapter 4 Elasticity Elasticity

2. 2 Example 4.1 Will the China’s trade balance (export – import) deteriorate if RMB appreciates (say, from 1USD=8.1RMB to 1USD=7.8RMB)? 1.China’s imports become less expensive. Quantity demanded for import may increase. 2.China’s Exports become more expensive. Quantity demanded for export may decrease. The impact of RMB appreciation on the trade balance depends on the responsiveness of import demand and export demand to the appreciation.

3. 3 Price Elasticity of Demand The Price Elasticity of Demand is a measure of the responsiveness of the quantity demanded of a good to a change in the price of that good. Formally, it is the percentage change in the quantity demanded that results from a 1 percent change in its price. Percentage change in quantity demanded Percentage change in price

4. 4 Elasticity Generally, elasticity is a measure of the responsiveness of the quantity demanded of a good to a change in the price of that good

5. 5 Example 4.2 The price of pork falls by 2% and the quantity demanded increases by 6% Then the price elasticity of demand for pork is Percentage change in quantity demanded Percentage change in price 6% -2% = -3-3

6. 6 Example 4.3. If a 1 percent rise in the price of shelter caused a 2 percent reduction in the quantity of shelter demanded, the price elasticity of demand for shelter would be -2% 1% = -2-2

7. 7 Price Elasticity of Demand Measuring Price Elasticity of Demand Observations Price elasticity of demand will always be negative (i.e., an inverse relationship between price and quantity). For convenience sometimes we drop the negative sign. Percentage change in quantity demanded Percentage change in price

8. 8 Price Elasticity of Demand 0 Price elasticity of demand Elastic Unit elastic inelastic -2-3

9. 9 Example 4.4. What is the elasticity of demand for sushi? Originally Price = $10/piece Quantity demanded = 400 pieces/day New Price = $9.7/piece Quantity demanded = 404 pieces/day, then Inelastic! (404 - 400)/400 (9.7 - 10)/10 = 1% -3% = -1 3

10. 10 Example 4.5. What is the elasticity of Hong Kong Disney passes? Originally Price = $1600 Quantity demanded = 10,000 passes/year New Price = $1520 Quantity demanded = 12,000 passes/year, then Elastic! (12000 - 10000)/10000 (1520 - 1600)/1600 = 20% -5% = -4

11. 11 Determinants of Price Elasticity of Demand 1.Availability of substitutes - the higher the number of substitutes, the more responsive people are to price changes. Elasticity increases with availability of substitutes. 2.Proportion of income used to buy the good - the higher the fraction of income spent on a good, the higher is elasticity. 3.Temporary versus permanent change in price - if the price change is temporary people react more to it. Suppose there is a one-day sale - the response of quantity demanded that day will be much greater than the response to quantity when prices are expected to decrease permanently. 4.Short run versus long run - elasticity increases over time. If there is a sudden price increase, individuals will take some time to find other substitutes and make suitable changes. So quantity will not respond much in the short run.

12. 12 Example 4.6. Price Elasticity Estimates for Selected Products Good or servicePrice elasticity Green peas-2.80 Restaurant meals-1.63 Automobiles-1.35 Electricity-1.20 Beer-1.19 Movies-0.87 Air travel (foreign)-0.77 Shoes-0.70 Coffee-0.25 Theater, opera-0.18 Why is the price elasticity of demand more than 14 times larger for green peas than for theater and opera performances?

13. 13 A Graphical Interpretation of Price Elasticity For small changes in price Where Q is the original quantity and P is the original price.

14. 14 A Graphical Interpretation of Price Elasticity For small changes in price Quantity Price P D A Q P - P Q + Q Q P

15. 15 Example 4.7. Calculating Price Elasticity of Demand 20 Quantity Price 1 D A 2345 16 12 8 4 Question: What is the price elasticity of demand when P = $8?

16. 16 Example 4.8. Price Elasticity and the Steepness of the Demand Curve D1D1 D2D2 12 46 6 4 Quantity Price What is the price elasticity of Demand for D 1 & D 2 when P = $4? Observation If two demand curves have a point in common, the steeper curve must be less elastic with respect to price at that point.

17. 17 Example 4.9. Price Elasticity Regions along a Straight-Line Demand Curve 12 D 461012 6 4 1 When P = $1 Quantity Price When P = $4 Observation Price elasticity varies at every point along a straight-line demand curve

18. 18 Price Elasticity Regions along a Straight-Line Demand Curve Quantity Price b/2 a/2 a b Observation Price elasticity varies at every point along a straight- line demand curve

19. 19 Perfectly Elastic Demand Curve Quantity Price If the price increases a little, the quantity demanded will drop to zero. If the price drops a little, the quantity demanded will increase a lot.

20. 20 Perfectly Inelastic Demand Curve Quantity Price The quantity demanded is not responsive to any change in price.

21. 21 Elasticity and Total Expenditure Total Expenditure = P x Q Market demand measures the quantity (Q) at each price (P) Total Expenditure = Total Revenue

22. 22 Example 4.10. The Demand Curve for Movie Tickets 12 Quantity (100s of tickets/day) Price ($/ticket) 13456 10 8 6 4 2 0 2 Total expenditure ($/day) 12 Price ($/ticket) 0 101000 81600 61800 41600 21000 00

23. 23 Total Expenditure as a Function of Price 1,800 Price ($/ticket) Total expenditure ($/day) 2681012 1,600 1,000 0 4 12 Quantity (100s of tickets/day) Price ($/ticket) 13456 10 8 6 4 2 0 2 Total revenue is at a maximum at the midpoint on a straight-line demand curve.

24. 24 Example 4.11. What happens to total expenditure on shelter when the price is reduced from $12/sq yd to $10/sq yd? When price goes down, total expenditure will rise [fall] if the gain from sale of additional units is larger [smaller] than the loss from the sale of existing units at the lower price.

25. 25 Example 4.12. Elasticity and Total Expenditure Should a rock band raise or lower its price to increase total revenue? Assume P=$20, Q=5,000, and  =-3. Total revenue = $20 x 5,000 = $100,000/week If P is increased 10%, Q will decrease 30% Total revenue = $22 x 3,500 = $77,000/week If P is lowered 10%, Q will increase 30% Total revenue = $18 x 6,500 = $177,000/week Note: Cost does not change with Q. Maximizing total revenue is the same as maximizing total profit.

26. 26 Elasticity and Total Expenditure

27. 27 A demand curve with constant elasticity Q P Unitary elastic: PxQ=k

28. 28 Example 4.13. A director of a big bus company said, "For each 1 percent fare hike, we lose 0.2 percent of our riders." We can conclude that: a. a fare increase will increase total revenue. b. demand for bus service will go up as fares increase. c. demand is price elastic. d. a 10 percent fare hike will produce a 20 percent reduction in riders. e. the price elasticity is -5. We are told that when  P/P = 1%,  Q/Q = -0.2%. Elasticity = (  Q/Q)/(  P/P) = -0.2. (inelastic) So answer a is correct. A fare increase will increase total revenue.

29. 29 Cross-Price Elasticity of Demand The percentage by which quantity demanded of the first good changes in response to a 1 percent change in the price of the second good Substitute Goods When the cross-price elasticity of demand is positive Complement Goods When the cross-price elasticity of demand is negative

30. 30 Income Elasticity of Demand The percentage by which quantity demanded changes in response to a 1 percent change in income Normal Goods Income elasticity is positive Inferior Goods Income elasticity is negative

31. 31 The Price Elasticity of Supply Price Elasticity of Supply The percentage change in the quantity supplied that occurs in response to a 1 percent change in price

32. 32 Example 4.14. A Supply Curve for Which Price Elasticity Declines as Quantity Rises 2 8 A 3 10 B Quantity Price 0 4 S 8 2 Observations: 1.Elasticity >0 2.Elasticity >1 for linear supply curve that has a positive Y-intercept. 3.Elasticity decreases as quantity increases.

33. 33 Example 4.15. A Supply Curve for Which Price Elasticity is unity S 15 5 B P Q 12 4 A Quantity Price 0 The price elasticity of supply will always equal 1 at any point along a straight-line supply curve that passes through the origin.

34. 34 A challenge Construct an example of supply curve so that price elasticity increases as quantity rises.

35. 35 A Perfectly Inelastic Supply Curve Quantity of land in Central (1,000s of acres) Price ($/acre) 0 S Elasticity = 0 at every point along a vertical supply curve What is the price elasticity of supply of land within Central?

36. 36 A Perfectly Elastic Supply Curve Quantity of lemonade (cups/day) Price (cents/cup) 0 14 S If MC is constant, then the price elasticity of supply at every point along a horizontal supply curve is infinite

37. 37 Determinants of Supply Elasticity 1.Flexibility of inputs 2.Mobility of inputs 3.Ability to produce substitute inputs 4.Time

38. 38 Example 4:16. Why are gasoline prices so much more volatile than car prices? Differences in markets Demand for gasoline is more inelastic Gasoline market has larger and more frequent supply shifts

39. 39 Greater Volatility in Gasoline Prices than in Car Prices Quantity (millions of gallons/day) Price ($/gallon) 0 6 1.69 S’ D 1.02 7.2 S Gasoline

40. 40 Greater Volatility in Gasoline Prices than in Car Prices Price ($1,000s/car) D 17 S’ 11 Quantity (1,000s of cars/day) Cars 16.4 12 S Cars

41. 41 Example 4.17. Earnings of YAO Ming Why does YAO Ming earn an annual basketball salary of some US$4.5 million? YAO Ming is a unique and essential inputs, an example of ultimate supply bottleneck.

42. 42 Other examples of unique and essential inputs Dr. Joseph YAM? Mr Mirko Saccani? “The fee was agreed to be $120 million for eight years' of unlimited [Latini]dance lessons and competitions, and Mr Saccani would be her dancing partner and instructor by such agreements.” (SCMP 2006-06-14, CITY3) Who was she, the plaintiff? Mimi Monica Wong, head of HSBC's private banking in Asia.

43. 43 Example 4.18. So why are the fares so different? If you start in Kansas City and you fly to Honolulu round-trip, the fare is a lot lower than if you start the same trip in Honolulu and fly to Kansas City round-trip. Passengers travel on same planes, consuming the same fuel, the same in-flight amenities, and so on. So why are the fares so different? By Karen Hittle, a student of Robert Frank.

44. 44 Example 4.18. So why are the fares so different? If you are starting in Kansas City and going to Honolulu, you are probably going on vacation. You could go lots of different places. You could go to Florida, to Barbados, to Cancun. Because vacationers have many destinations to choose from, airlines must compete fiercely for their business. Given economies of scale inherent in larger aircraft, carriers have a strong incentive to fill additional seats by targeting lower prices to the people who are more sensitive to price – vacationers. But if you are starting in Honolulu on a trip to Kansas City, you are probably not a vacationer. More likely, you either have business or family reasons for traveling. So you are probably not shopping for a destination if you are going to Kansas City. That is why the fares are so different.

45. 45 Example 4.19. Other things being equal, the increase in rents that occur after rent control are abolished is smaller when A.the own price elasticity of demand for rental homes is price inelastic. B.the own price elasticity of demand for rental homes is price elastic. C.the own price elasticity of demand for rental homes has unitary price elasticity. D.rented homes and owned homes are substitutes. E.rented homes and owned homes are complements.

46. 46 Example 4.19. Rent control is a form of PRICE CEILING. Price Ceiling is set at a price LOWER than the market equilibrium price. Excess demand (i.e., shortage) results. P Q DS PePe Price Ceiling Trading Loci

47. 47 Example 4.19. And when the Price Ceiling is lifted, the market equilibrium quantity and price should be restored eventually. Price (rent) should increase. P Q DS Price Ceiling Because supply is upward sloping, ↑ P → ↑ TR

48. 48 P Q DS PePe Price Ceiling Relative inelastic Relative elastic Hence, the increase in rents that occur AFTER abolishing rent control is smaller when (B) The own price elasticity of demand is elastic. Example 4.19.

49. 49 End