1. © 2007 Thomson South-Western, all rights reserved N. G R E G O R Y M A N K I W PowerPoint ® Slides by Ron Cronovich 5 P R I N C I P L E S O F F O U R T H E D I T I O N Elasticity and its Application

2. 1 CHAPTER 5 ELASTICITY AND ITS APPLICATION Why is Elasticity Important? To measure the magnitude of changes.  Laws of Supply and Demand tell the direction of changes. To determine magnitudes, we need to know the precise shapes of curves.  Elasticity measures how much one variable responds to another.  Knowing price elasticities allows us to measure the magnitude of changes as markets evolve – future prices, quantities, and the total size of markets (total spending).  Such predictions can assist firms in making decisions. Governments also use this information to predict how public policies may affect markets (e.g. impose taxes)

3. 2 CHAPTER 5 ELASTICITY AND ITS APPLICATION You design websites for local businesses. You charge $200 per website, and currently sell 12 websites per month. Your costs are rising (including the opp. cost of your time), so you’re thinking of raising the price to $250. The law of demand says that you would sell less. How many fewer websites? How much will your revenue fall, or might it actually increase? You design websites for local businesses. You charge $200 per website, and currently sell 12 websites per month. Your costs are rising (including the opp. cost of your time), so you’re thinking of raising the price to $250. The law of demand says that you would sell less. How many fewer websites? How much will your revenue fall, or might it actually increase? A business scenario…

4. 3 CHAPTER 5 ELASTICITY AND ITS APPLICATION Price Elasticity of Demand: (Elasticity measures how much one variable responds to a change in another variable)  Price elasticity of demand measures how much Q d responds to a change in P. Price elasticity of demand = Percentage change in Q d Percentage change in P  Loosely speaking, it measures the price- sensitivity of buyers’ demand, and it reflects in part the slope of the demand curve.

5. 4 CHAPTER 5 ELASTICITY AND ITS APPLICATION Price Elasticity of Demand Price elasticity of demand equals P Q D Q2Q2 P2P2 P1P1 Q1Q1 P rises by 10% Q falls by 15% 15% 10% = 1.5 Price elasticity of demand = Percentage change in Q d Percentage change in P Example:

6. 5 CHAPTER 5 ELASTICITY AND ITS APPLICATION Your Web Site Business Again (Price Elasticity and Total Revenue)  If you raise your price from $200 to $250, would your revenue rise or fall? Revenue = P x Q  A price increase has two effects on revenue: Higher P means more revenue on each unit you sell. But you sell fewer units (lower Q)  Which of these two effects is bigger? It depends on the price elasticity of demand.

7. 6 CHAPTER 5 ELASTICITY AND ITS APPLICATION Price Elasticity and Total Revenue -- here the answer is unfavorable! But, Elastic demand (elasticity = 1.8) P Q D $200 12 If P = $200, Q = 12 and revenue = $2400. When D is elastic, a price increase causes revenue to fall. $250 8 If P = $250, Q = 8 and revenue = $2000. lost revenue due to lower Q increased revenue due to higher P Demand for your websites

8. 7 CHAPTER 5 ELASTICITY AND ITS APPLICATION Calculating Demand Elasticities: starting with Percentage Changes P Q D $250 8 B $200 12 A Demand for your websites Standard method of computing the percentage (%) change: end value – start value start value x 100% Going from A to B, the % change in P equals ($250–$200)/$200 = 25%

9. 8 CHAPTER 5 ELASTICITY AND ITS APPLICATION Calculating Percentage Changes: the problem of deciding which point is the ‘starting’ point: old price or new price?  We instead use the midpoint method: end value – start value midpoint x 100%  The midpoint is the number halfway between the start & end values, or the average.  It doesn’t matter which value you use as the “start” and which as the “end” – you get the same answer either way!

10. 9 CHAPTER 5 ELASTICITY AND ITS APPLICATION Calculating Percentage Changes  Using the midpoint method, the % change in P equals $250 – $200 $225 x 100% = 22.2%  The % change in Q equals 12 – 8 10 x 100% = 40.0%  The price elasticity of demand equals 40/22.2 = 1.8

11. A C T I V E L E A R N I N G 1 : Calculate an elasticity Use the following information to calculate the price elasticity of demand for hotel rooms: if P = $70, Q d = 5000 if P = $90, Q d = 3000 10

12. A C T I V E L E A R N I N G 1 : Answers Use midpoint method to calculate % change in Q d (5000 – 3000)/4000 = 50% % change in P ($90 – $70)/$80 = 25% The price elasticity of demand equals 11 50% 25% = 2.0

13. 12 CHAPTER 5 ELASTICITY AND ITS APPLICATION The Determinants of Price Elasticity: A Summary The price elasticity of demand depends on:  the extent to which close substitutes are available  whether the good is a necessity or a luxury  how broadly or narrowly the good is defined  the time horizon: elasticity is higher in the long run than the short run. (People have time to make adjustments over time.) The price elasticity of demand depends on:  the extent to which close substitutes are available  whether the good is a necessity or a luxury  how broadly or narrowly the good is defined  the time horizon: elasticity is higher in the long run than the short run. (People have time to make adjustments over time.)

14. 13 CHAPTER 5 ELASTICITY AND ITS APPLICATION Examples: what determines price elasticity? Compare some common examples. In each case, prices of both goods increase by 20%. The good for which Q d falls the most (in percent) has the highest price elasticity of demand. Which good is it? Why? * Rice Crispies vs. Sunscreen * Insulin vs. Caribbean cruises * Gasoline in the short run v. in the long run

15. 14 CHAPTER 5 ELASTICITY AND ITS APPLICATION Explaining the elasticities:  Rice Crispies vs. sunscreen: There are many substitute cereals, but no close substitute for sunscreen. Elasticity high when close substitutes exist (e.g. Rice Crispies)!  Insulin vs. cruise: Insulin is a necessity for a diabetic, while a cruise is a luxury for most. Elasticities are low for necessities (e.g. insulin)!  Gas in the short or long run: Few choices to driving in the short run, but with more time people can alter their location and car choice. Price elasticity is higher in the long run!

16. 15 CHAPTER 5 ELASTICITY AND ITS APPLICATION Price elasticities for Econ 200 Class  Rank from highest to lowest price elasticity (i.e., most to least price sensitive) -- “high” elasticity, “about one”, “low” elasticity: Warmer winter coat Computer Cell phone Pizza delivered to dorm/room Laundry room machine use Maryland hats/t-shirts/shorts, etc levis

17. 16 CHAPTER 5 ELASTICITY AND ITS APPLICATION The Variety of Demand Curves  Economists classify demand curves according to their elasticity.  The price elasticity of demand is closely related to the slope of the demand curve.  Two broad cases: If the demand curve is quite flat, quantity demanded is very responsive to price. Flatter curves have bigger elasticities. We call this “elastic demand”.  The reverse case of a steep curve, quantity is not very responsive to price. Steep curves have smaller elasticities. We call this “inelastic demand.”

18. 17 CHAPTER 5 ELASTICITY AND ITS APPLICATION D “Inelastic demand” P Q Q1Q1 P1P1 Q2Q2 P2P2 Q rises less than 10% < 10% 10% < 1 Price elasticity of demand = % change in Q % change in P = P falls by 10% Consumers’ price sensitivity: D curve: Elasticity: relatively steep relatively low < 1

19. 18 CHAPTER 5 ELASTICITY AND ITS APPLICATION D “Elastic demand” P Q Q1Q1 P1P1 Q2Q2 P2P2 Q rises more than 10% > 10% 10% > 1 Price elasticity of demand = % change in Q % change in P = P falls by 10% Consumers’ price sensitivity: D curve: Elasticity: relatively flat relatively high > 1

20. 19 CHAPTER 5 ELASTICITY AND ITS APPLICATION Q1Q1 P1P1 D “Perfectly inelastic demand” (one extreme case) P Q P2P2 P falls by 10% Q changes by 0% 0% 10% = 0 Price elasticity of demand = % change in Q % change in P = Consumers’ price sensitivity: D curve: Elasticity: vertical 0 0

21. 20 CHAPTER 5 ELASTICITY AND ITS APPLICATION How Elasticity affects Total Revenue – in words. INELASTIC DEMAND (Less than one): Raising price has little effect on quantity demanded (the %age fall in quantity is LESS THAN the %age rise in price) – hence total revenue up.  ELASTIC DEMAND (more than one): Raising price results in large fall in quantity (the %age fall is quantity is MORE THAN the %age rise in price) – hence total revenue falls.  Memory Hint: Inelastic demand, buyers do not respond much to prices, so raise price and raise total revenue! The reverse: elastic demand, buyers very responsive to price, set prices lower and sell much more to raise rev.

22. 21 CHAPTER 5 ELASTICITY AND ITS APPLICATION Revenue and Elasticity again – the math!  Revenue = (P)(Q)  A simple rule from mathematics: %change Revenue = %ch (P) + %ch (Q)  You raise price: ch(P) is + ch(Q) is --  So revenue up if: %ch(P) bigger than %ch(Q).  When is this true??  elast of demand = %ch(Q) / %ch(P) if elast LT 1, % ch(Q) LT %ch(P) and, if elast GT 1, %ch(Q) LT %ch(P)

23. 22 CHAPTER 5 ELASTICITY AND ITS APPLICATION Elasticity of a Linear Demand Curve The slope of a linear demand curve is constant, but its elasticity is not. P Q $30 20 10 $0 0204060 200% 40% = 5.0 E =E = 67% = 1.0 E =E = 40% 200% = 0.2 E =E =

24. A C T I V E L E A R N I N G 2 : Elasticity and expenditure/revenue * What do you need to know to answer this question?? A. Pharmacies raise the price of insulin by 10%. Does total expenditure on insulin rise or fall? B. As a result of a fare war, the price of a luxury cruise falls 20%. Does luxury cruise companies’ total revenue rise or fall? 23

25. A C T I V E L E A R N I N G 2 : Answers to effect on total revenue….. 24 A. Pharmacies raise the price of insulin by 10%. Does total expenditure on insulin rise or fall? Expenditure = P x Q Since demand is inelastic, Q will fall less than 10%, so expenditure rises. B. Cruise prices fall by 20%. If demand is elastic, Q rises more than 20%, so expenditure falls.

26. 25 CHAPTER 5 ELASTICITY AND ITS APPLICATION APPLICATION: Does Drug Interdiction Increase or Decrease Drug-Related Crime?  One side effect of illegal drug use is crime: Users often turn to crime to finance their habit.  We examine two policies designed to reduce illegal drug use and see what effects they have on drug-related crime.  For simplicity, we assume the total dollar value of drug-related crime equals total expenditure on drugs.  Demand for illegal drugs is inelastic, due to addiction issues.

27. 26 CHAPTER 5 ELASTICITY AND ITS APPLICATION Policy 1: Interdiction Price of Drugs Quantity of Drugs S1S1 S2S2 D1D1 P1P1 Q1Q1 P2P2 Q2Q2 Interdiction reduces the supply of drugs. Since demand for drugs is inelastic, P rises propor- tionally more than Q falls. Result: an increase in total spending on drugs, and in drug-related crime new value of drug- related crime initial value of drug- related crime

28. 27 CHAPTER 5 ELASTICITY AND ITS APPLICATION Policy 2: Education Price of Drugs Quantity of Drugs D1D1 S P1P1 Q1Q1 D2D2 P2P2 Q2Q2 Education reduces the demand for drugs. P and Q fall. Result: A decrease in total spending on drugs, and in drug-related crime. initial value of drug- related crime new value of drug- related crime

29. 28 CHAPTER 5 ELASTICITY AND ITS APPLICATION Price Elasticity of Supply  Price elasticity of supply measures how much Q s responds to a change in P. Price elasticity of supply = Percentage change in Q s Percentage change in P  Loosely speaking, it measures the price- sensitivity of sellers’ supply.  Again, use the midpoint method to compute the percentage changes.

30. 29 CHAPTER 5 ELASTICITY AND ITS APPLICATION Q2Q2 Price Elasticity of Supply Price elasticity of supply equals P Q S P2P2 Q1Q1 P1P1 P rises by 8% Q rises by 16% 16% 8% = 2.0 Price elasticity of supply = Percentage change in Q s Percentage change in P Example:

31. 30 CHAPTER 5 ELASTICITY AND ITS APPLICATION The Variety of Supply Curves  Economists ‘classify’ supply curves according to their elasticity.  The slope of the supply curve is closely related to price elasticity of supply.  Rule of thumb: The flatter the curve, the bigger the elasticity (along much of the curve). The steeper the curve, the smaller the elasticity.  The next two slides present different classifications, from least to most elastic.

32. 31 CHAPTER 5 ELASTICITY AND ITS APPLICATION S “Inelastic” P Q Q1Q1 P1P1 Q2Q2 P2P2 Q rises less than 10% < 10% 10% < 1 Price elasticity of supply = % change in Q % change in P = P rises by 10% Sellers’ price sensitivity: S curve: Elasticity: relatively steep relatively low < 1

33. 32 CHAPTER 5 ELASTICITY AND ITS APPLICATION S “Elastic” P Q Q1Q1 P1P1 Q2Q2 P2P2 Q rises more than 10% > 10% 10% > 1 Price elasticity of supply = % change in Q % change in P = P rises by 10% Sellers’ price sensitivity: S curve: Elasticity: relatively flat relatively high > 1

34. 33 CHAPTER 5 ELASTICITY AND ITS APPLICATION S “Perfectly inelastic” (one extreme) P Q Q1Q1 P1P1 P2P2 Q changes by 0% 0% 10% = 0 Price elasticity of supply = % change in Q % change in P = P rises by 10% Sellers’ price sensitivity: S curve: Elasticity: vertical 0 0

35. 34 CHAPTER 5 ELASTICITY AND ITS APPLICATION The Determinants of Supply Elasticity  The more easily sellers can change the quantity they produce, the greater the price elasticity of supply.  Example: Supply of beachfront property is harder to vary and thus less elastic than supply of new cars.  For many goods, price elasticity of supply is greater in the long run than in the short run, because firms can build new factories, or new firms may be able to enter the market.

36. A C T I V E L E A R N I N G 3 : Elasticity and changes in equilibrium  The supply of beachfront property is inelastic. The supply of new cars is elastic.  Suppose population growth causes demand for both goods to double (at each price, Q d doubles).  For which product will P change the most?  For which product will Q change the most? 35

37. A C T I V E L E A R N I N G 3 : Answers 36 Beachfront property (inelastic supply): P Q D1D1 D2D2 S Q1Q1 P1P1 A B Q2Q2 P2P2 When supply is inelastic, an increase in demand has a bigger impact on price than on quantity.

38. A C T I V E L E A R N I N G 3 : Answers 37 New cars (elastic supply): P Q D1D1 D2D2 S Q1Q1 P1P1 A Q2Q2 P2P2 B When supply is elastic, an increase in demand has a bigger impact on quantity than on price.

39. 38 CHAPTER 5 ELASTICITY AND ITS APPLICATION Other Elasticities  The income elasticity of demand measures the response of Q d to a change in consumer income. Income elasticity of demand = Percent change in Q d Percent change in income  Recall from chap.4: An increase in income causes an increase in demand for a normal good.  Hence, for normal goods, income elasticity > 0.  For inferior goods, income elasticity < 0.

40. 39 CHAPTER 5 ELASTICITY AND ITS APPLICATION CHAPTER SUMMARY  Elasticity measures the responsiveness of Q d or Q s to one of its determinants.  Price elasticity of demand equals percentage change Q d in divided by percentage change in P. When it’s less than one, demand is “inelastic.” When greater than one, demand is “elastic.”  When demand is inelastic, total revenue rises when price rises. When demand is elastic, total revenue falls when price rises.

41. 40 CHAPTER 5 ELASTICITY AND ITS APPLICATION CHAPTER SUMMARY  Demand is less elastic in the short run, for necessities, for broadly defined goods, or for goods with few close substitutes.  Price elasticity of supply is greater in the long run than in the short run.  Income elasticity of demand measures how much quantity demanded responds to changes in income. Income elasticities are positive for normal goods and negative for inferior goods.