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• The elasticity chapter in most principles textbooks is fairly technical, and is not always students’ favorite. This PowerPoint chapter contains several special features designed to engage and motivate students to learn this important material. First, we consider a scenario in which students face a business decision – whether to raise the price of a service they sell. This scenario is used to illustrate the effects of raising price on number of units sold and on revenue, which students immediately recognize as critical to the business decision. Second, instead of merely listing the determinants of elasticity, students are asked to think about some concrete examples and deduce from each one a lesson about the determinants of elasticity. Third, instead of putting the applications at the end of the chapter (as in the textbook), this PowerPoint includes one of them immediately after the section on price elasticity of demand. This helps break up what would otherwise be a long stretch of theory. Please be assured that this PowerPoint presentation is, nonetheless, very consistent with the textbook.
• We will follow this scenario throughout the first section of this chapter (the section on price elasticity of demand) to illustrate and motivate several important concepts, such as the impact of price changes on sales and revenue.
• Here, Q d and Q s are short for quantity demanded and quantity supplied, as in the PowerPoint for Chapter 4.
• It might be worth explaining to your students that “P and Q move in opposite directions” means that the percentage change in Q and the percentage change in P will have opposite signs, thus implying a negative price elasticity. To be consistent with the text, the last statement in the green box says that we will report all price elasticities as positive numbers. It might be slightly more accurate to say that we will report all elasticities as non-negative numbers: we want to allow for the (admittedly rare) case of zero elasticity.
• These calculations are based on the example shown a few slides back: points A and B on the website demand curve.
• In essence, the textbook says “Here are the determinants of elasticity. The first one is availability of close substitutes. Here’s an example….” That’s great for a textbook. For teaching, I’ve found a different approach to be far more effective – the approach on the following four slides, which essentially has students deduce the general lessons from specific examples that students can probably figure out with a little common sense. See notes on the next slide for a good suggestion.
• Suggestion: For each of these examples, display the slide title (which lists the two goods) and the first two lines of text (which ask which good experiences the biggest drop in demand in response to a 20% price increase). Give your students a quiet minute to formulate their answers. Then, ask for volunteers.
• You might need to clarify the nature of this thought experiment. Here, we look at two alternate scenarios. In the first, the price of blue jeans (and no other clothing) rises by 20%, and we observe the percentage decrease in quantity of blue jeans demanded. In the second scenario, the price of all clothing rises by 20%, and we observe the percentage decrease in demand for all clothing.
• This slide is a convenience for your students, and replicates a similar table from the text. If you’re pressed for time, it is probably safe to omit this slide from your presentation.
• If Q doesn’t change, then the percentage change in Q equals zero, and thus elasticity equals zero. It is hard to think of a good for which the price elasticity of demand is literally zero. Take insulin, for example. A sufficiently large price increase would probably reduce demand for insulin a little, particularly among people with very low incomes and no health insurance. However, if elasticity is very close to zero, then the demand curve is almost vertical. In such cases, the convenience of modeling demand as perfectly inelastic probably outweighs the cost of being slightly inaccurate.
• An example: student demand for textbooks that their professors have required for their courses. Here, it’s a little more clear that elasticity would be small, but not zero. At a high enough price, some students will not buy their books, but instead will share with a friend, or try to find them in the library, or just take copious notes in class. Another example: gasoline in the short run.
• This is the intermediate case: the demand curve is neither relatively steep nor relatively flat. Buyers are neither relatively price-sensitive nor relatively insensitive to price. This is also the case where price changes have no effect on revenue.
• A good example here would be Rice Krispies, or nearly anything with readily available substitutes. An elastic demand curve is flatter than a unit elastic demand curve (which itself is flatter than an inelastic demand curve).
• “ Extreme price sensitivity” means the tiniest price increase causes demand to fall to zero. “ Q changes by any %” – when the D curve is horizontal, the quantity is indeterminant. Consumers might demand Q1 units one month, Q2 units another month, and some other quantity later. Q can change by any amount, but P always “changes by 0%” (i.e. doesn’t change). If perfectly inelastic is one extreme, this (perfectly elastic) is the other. Here’s a good real-world example of a perfectly elastic demand curve, which foreshadows an upcoming chapter on firms in competitive markets. Suppose you run a small family farm in Iowa. Your main crop is wheat. The demand curve in this market is downward-sloping, and the market demand and supply curves determine the price of wheat. Suppose that price is \$5/bushel. Now consider the demand curve facing you, the individual wheat farmer. If you charge a price of \$5, you can sell as much or as little as you want. If you charge a price even just a little higher than \$5, demand for YOUR wheat will fall to zero: Buyers would not be willing to pay you more than \$5 when they could get the same wheat elsewhere for \$5. Similarly, if you drop your price below \$5, then demand for YOUR wheat will become enormous (not literally infinite, but “almost infinite”): if other wheat farmers are charging \$5 and you charge less, then EVERY buyer will want to buy wheat from you. Why is the demand curve facing an individual producer perfectly elastic? Recall that elasticity is greater when lots of close substitutes are available. In this case, you are selling a product that has many perfect substitutes: the wheat sold by every other farmer is a perfect substitute for the wheat you sell.
• The material on this slide is not used anywhere else in the textbook. Therefore, if you are pressed for time and looking for things to cut, you might consider cutting this slide. (Note that this is my personal recommendation and is not necessarily the official position of Greg Mankiw or Thomson/South-Western.) Due to space limitations, this slide uses “E” as an abbreviation for elasticity, or more specifically, the price e lasticity of demand, and the slide omits the analysis of revenue along the demand curve. Calculations of percentage changes use the midpoint method. (This is why the increase from Q=0 to Q=20 is 200% rather than infinity.) As you move down a linear demand curve, the slope (the ratio of the absolute change in P to that in Q) remains constant: From the point (0, \$30) to the point (20, \$20), the “rise” equals -\$10, the “run” equals +20, so the slope equals -1/2 or -0.5. From the point (40, \$10) to the point (60, \$0), the “rise” again equals -\$10, the “run” equals +20, and the slope again equals -0.5. However, the percentage changes in these variables do not remain constant, as shown by the different colored elasticity calculations that appear on the slide. The lesson here is that elasticity falls as you move downward &amp; rightward along a linear demand curve.
• We return to our scenario. It’s not hard for students to imagine being in this position – running their own business and trying to decide whether to raise the price. To most of your students, it should be clear that making the best possible decision would require information about the likely effects of the price increase on revenue. That is why elasticity is so helpful, as we will now see….
• In the “Normal” view (edit mode), the labels over the graph look cluttered, like they’re on top of each other. This is not a mistake – in “Slide Show” mode (presentation mode), they will be fine – try it! Point out to students that the area (outlined in blue) representing lost revenue due to lower Q is larger than the area (outlined in yellow) representing increased revenue due to higher P. Hence, the net effect is a fall in revenue.
• Again, the slide appears cluttered in “Normal” view (edit mode), but everything is fine when displayed in “Slide Show” mode (presentation mode). Point out to students that the area representing lost revenue due to lower Q is smaller than the area representing increased revenue due to higher P. Hence, the net effect is an increase in revenue. The knife-edge case, not shown here but worth mentioning in class, is unit-elastic demand. In that case, an increase in price leaves revenue unchanged: the increase in revenue from higher P exactly offsets the lost revenue due to lower Q.
• These problems, perhaps similar to those you might ask on an exam, are complex in that they test several skills at once: Students must determine whether demand for each good is elastic or inelastic, and they must determine the impact of a price change on revenue/expenditure. So far, we’ve been talking about how elasticity determines the effects of an increase in P on revenue. Part (b) asks your students to determine the effects of a decrease in P.
• The first part of the explanation discusses the opposing effects on revenue; its purpose is to clarify the effects of a price decrease on revenue, as we have previously only discussed the effects of a price increase.
• In the textbook, this application appears near the end of the chapter, and you can easily move these slides to the end if you wish to teach things in the same order as the book. However, I encourage you to consider teaching this application right here - immediately after the section on price elasticity of demand. It is safe to do so, as this application only requires knowledge of price elasticity of demand. Also, putting the application here breaks up what would otherwise be a very long section of theory with a real-world example that most students find very interesting. Knowing elasticity helps us understand what might otherwise be a counter-intuitive result (that drug interdiction increases drug-related crime rather than reducing it).
• By the time all elements have appeared on the screen, the slide will look kind of busy. I think this is okay, because the elements appear on the screen one by one, so students have time to absorb each one before the next one appears. However, if you’d rather strip the slide down a bit, here’s a suggestion: in “Normal” view (which is used to edit slides), you can delete the boxes that represent the initial and new values of drug-related crime, and the accompanying captions. Then, when presenting this slide in class, simply point out (with your mouse cursor, a laser pointer, or even your arms and hands) the areas that represent the initial and new values of drug-related crime.
• Most everything in the “price elasticity of supply” section corresponds to analogous concepts from the “price elasticity of demand” section. So, it is probably safe to move through this section more quickly.
• This section is not perfectly analogous to the section on the determinants of the price elasticity of demand, but it’s similar enough that you can probably cover it more quickly and with less hand-holding.
• This is one of the “Problems and Applications” at the end of the chapter.
• In this slide and the next, the initial price and quantity and the two demand curves are the same. The only difference is the elasticity of supply and slope of the supply curve. [The D curve shifts to the right, but not in a parallel fashion: at each price, quantity demanded is twice as high, so the new D curve will be flatter than the initial one.] In the text box containing the verbal explanation, “bigger impact” is shorthand for “bigger percentage impact” or “bigger proportional impact.”
• This graph replicates the one in Figure 6. Note: The graph here is not quite drawn to scale. When the price rises from \$3 to \$4 (a 29% increase, using the midpoint method), quantity rises from 100 to 120 (or 67%). Because 67% &gt; 29%, price elasticity of supply is greater than one. When the price rises from \$12 to \$15 (22%), quantity rises from 500 to 525 (about 5%), so price elasticity of supply is less than one. The way I like to explain this is as follows: When output is very low, it is relatively easy for firms to increase output. They may have excess capacity, or they are not requiring full effort from their workers. Increasing output is not difficult, so it doesn’t take much of an increase in price to induce an increase in production. When output is very high, it is relatively expensive for firms to increase output further: there’s little or no excess capacity, they are already running their factories and machines at a high level of intensity. To increase output further, they might have to pay their workers overtime, and their machines experience more wear and tear and therefore require more repairs. So, at high levels of output, it takes a much larger price increase to make firms willing to increase output further. Eventually, firms bump up against their capacity constraints, and simply cannot increase output in response to further price increases. Of course, all of this applies to the short run. In the long run, firms can build more factories, and (depending on the market structure) new firms can enter the market.
• This topic and the next one (cross-price elasticity) do not appear anywhere else in the book. Instructors who are pressed for time may consider cutting these topics. (This is not the official position of Greg Mankiw or Thomson/South-Western, it’s just my suggestion.)
• ### Micro ch05-presentation

1. 1. 5 Elasticity and its Application PRINCIPLES OF MICROECONOMICS FOURTH EDITION N. G R E G O R Y M A N K I W PowerPoint® Slides by Ron Cronovich © 2007 Thomson South-Western, all rights reserved
2. 2. In this chapter, look for the answers tothese questions:  What is elasticity? What kinds of issues can elasticity help us understand? What is the price elasticity of demand? How is it related to the demand curve? How is it related to revenue & expenditure? What is the price elasticity of supply? How is it related to the supply curve? What are the income and cross-price elasticities of demand? CHAPTER 5 ELASTICITY AND ITS APPLICATION 2
3. 3. 0 A scenario…You design websites for local businesses.You charge \$200 per website, and currently sell12 websites per month.Your costs are rising (including the opp. cost ofyour time), so you’re thinking of raising the priceto \$250.The law of demand says that you won’t sell asmany websites if you raise your price. How manyfewer websites? How much will your revenue fall,or might it increase?CHAPTER 5 ELASTICITY AND ITS APPLICATION 3
4. 4. 0 Elasticity Basic idea: Elasticity measures how much one variable responds to changes in another variable. • One type of elasticity measures how much demand for your websites will fall if you raise your price. Definition: Elasticity is a numerical measure of the responsiveness of Qd or Qs to one of its determinants.CHAPTER 5 ELASTICITY AND ITS APPLICATION 4
5. 5. 0 Price Elasticity of Demand Price elasticity Percentage change in Qd = of demand Percentage change in P Price elasticity of demand measures how much Qd responds to a change in P. Loosely speaking, it measures the price- sensitivity of buyers’ demand.CHAPTER 5 ELASTICITY AND ITS APPLICATION 5
6. 6. 0 Price Elasticity of Demand Price elasticity Percentage change in Qd = of demand Percentage change in P P Example: P rises Price P2 by 10% elasticity P1 of demand D equals Q 15% Q2 Q1 = 1.5 Q falls 10% by 15%CHAPTER 5 ELASTICITY AND ITS APPLICATION 6
7. 7. 0 Price Elasticity of Demand Price elasticity Percentage change in Qd = of demand Percentage change in P PAlong a D curve, P and Qmove in opposite directions, P2which would make priceelasticity negative. P1We will drop the minus sign Dand report Qall price elasticities Q2 Q1as positive numbers.CHAPTER 5 ELASTICITY AND ITS APPLICATION 7
8. 8. 0 Calculating Percentage Changes Standard method of computing the Demand for percentage (%) change: your websites P end value – start value x 100% start value B\$250 A Going from A to B,\$200 the % change in P equals D (\$250–\$200)/\$200 = 25% Q 8 12 CHAPTER 5 ELASTICITY AND ITS APPLICATION 8
9. 9. 0 Calculating Percentage Changes Problem: The standard method gives Demand for different answers depending your websites on where you start. P From A to B, B P rises 25%, Q falls 33%,\$250 A elasticity = 33/25 = 1.33\$200 D From B to A, P falls 20%, Q rises 50%, Q 8 12 elasticity = 50/20 = 2.50 CHAPTER 5 ELASTICITY AND ITS APPLICATION 9
10. 10. 0 Calculating Percentage Changes So, we instead use the midpoint method: end value – start value x 100% midpoint The midpoint is the number halfway between the start & end values, also the average of those values. It doesn’t matter which value you use as the “start” and which as the “end” – you get the same answer either way!CHAPTER 5 ELASTICITY AND ITS APPLICATION 10
11. 11. 0 Calculating Percentage Changes Using the midpoint method, the % change in P equals \$250 – \$200 x 100% = 22.2% \$225 The % change in Q equals 12 – 8 x 100% = 40.0% 10 The price elasticity of demand equals 40/22.2 = 1.8CHAPTER 5 ELASTICITY AND ITS APPLICATION 11
12. 12. 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, Qd = 5000 if P = \$90, Qd = 3000 12
13. 13. A C T I V E L E A R N I N G 1:AnswersUse midpoint method to calculate % change in Qd (5000 – 3000)/4000 = 50%% change in P (\$90 – \$70)/\$80 = 25%The price elasticity of demand equals 50% = 2.0 25% 13
14. 14. 0 What determines price elasticity?To learn the determinants of price elasticity,we look at a series of examples.Each compares two common goods.In each example: • Suppose the prices of both goods rise by 20%. • The good for which Qd falls the most (in percent) has the highest price elasticity of demand. Which good is it? Why? • What lesson does the example teach us about the determinants of the price elasticity of demand?CHAPTER 5 ELASTICITY AND ITS APPLICATION 14
15. 15. EXAMPLE 1: 0Rice Krispies vs. Sunscreen The prices of both of these goods rise by 20%. For which good does Qd drop the most? Why? • Rice Krispies has lots of close substitutes (e.g., Cap’n Crunch, Count Chocula), so buyers can easily switch if the price rises. • Sunscreen has no close substitutes, so consumers would probably not buy much less if its price rises. Lesson: Price elasticity is higher when close substitutes are available.CHAPTER 5 ELASTICITY AND ITS APPLICATION 15
16. 16. EXAMPLE 2: 0“Blue Jeans” vs. “Clothing”  The prices of both goods rise by 20%. For which good does Qd drop the most? Why? • For a narrowly defined good such as blue jeans, there are many substitutes (khakis, shorts, Speedos). • There are fewer substitutes available for broadly defined goods. (Can you think of a substitute for clothing, other than living in a nudist colony?)  Lesson: Price elasticity is higher for narrowly defined goods than broadly defined ones.CHAPTER 5 ELASTICITY AND ITS APPLICATION 16
17. 17. EXAMPLE 3: 0Insulin vs. Caribbean Cruises The prices of both of these goods rise by 20%. For which good does Qd drop the most? Why? • To millions of diabetics, insulin is a necessity. A rise in its price would cause little or no decrease in demand. • A cruise is a luxury.If the price rises, some people will forego it. Lesson: Price elasticity is higher for luxuries than for necessities.CHAPTER 5 ELASTICITY AND ITS APPLICATION 17
18. 18. EXAMPLE 4: 0Gasoline in the Short Run vs. Gasoline inthe Long Run The price of gasoline rises 20%. Does Qd drop more in the short run or the long run? Why? • There’s not much people can do in the short run, other than ride the bus or carpool. • In the long run, people can buy smaller cars or live closer to where they work. Lesson: Price elasticity is higher in the long run than the short run.CHAPTER 5 ELASTICITY AND ITS APPLICATION 18
19. 19. The Determinants of Price Elasticity: 0 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.CHAPTER 5 ELASTICITY AND ITS APPLICATION 19
20. 20. 0 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. Rule of thumb: The flatter the curve, the bigger the elasticity. The steeper the curve, the smaller the elasticity. The next 5 slides present the different classifications, from least to most elastic.CHAPTER 5 ELASTICITY AND ITS APPLICATION 20
21. 21. 0“Perfectly inelastic demand” (one extreme case) Price elasticity % change in Q 0% = = =0 % change in P 10% of demandD curve: P D vertical P1Consumers’price sensitivity: P2 0 P falls QElasticity: by 10% Q1 0 Q changes by 0%CHAPTER 5 ELASTICITY AND ITS APPLICATION 21
22. 22. 0“Inelastic demand” Price elasticity % change in Q < 10% = = <1 % change in P 10% of demandD curve: P relatively steep P1Consumers’price sensitivity: P2 relatively low D P falls QElasticity: by 10% Q1 Q2 <1 Q rises less than 10%CHAPTER 5 ELASTICITY AND ITS APPLICATION 22
23. 23. 0“Unit elastic demand” Price elasticity % change in Q 10% = = =1 % change in P 10% of demandD curve: P intermediate slope P1Consumers’price sensitivity: P2 D intermediate P falls QElasticity: by 10% Q1 Q2 1 Q rises by 10%CHAPTER 5 ELASTICITY AND ITS APPLICATION 23
24. 24. 0“Elastic demand” Price elasticity % change in Q > 10% = = >1 % change in P 10% of demandD curve: P relatively flat P1Consumers’price sensitivity: P2 D relatively high P falls QElasticity: by 10% Q1 Q2 >1 Q rises more than 10%CHAPTER 5 ELASTICITY AND ITS APPLICATION 24
25. 25. 0“Perfectly elastic demand” (the other extreme) Price elasticity % change in Q any % = = = infinity % change in P 0% of demandD curve: P horizontal P2 = P1 DConsumers’price sensitivity: extreme P changes QElasticity: by 0% Q1 Q2 infinity Q changes by any %CHAPTER 5 ELASTICITY AND ITS APPLICATION 25
26. 26. Elasticity of a Linear Demand Curve 0 P The slope 200% of a linear\$30 E = = 5.0 40% demand 67% curve is 20 E = = 1.0 67% constant, but its 40% 10 E = = 0.2 elasticity 200% is not. \$0 Q 0 20 40 60CHAPTER 5 ELASTICITY AND ITS APPLICATION 26
27. 27. Price Elasticity and Total Revenue 0 Continuing our scenario, 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), due to Law of Demand. Which of these two effects is bigger? It depends on the price elasticity of demand.CHAPTER 5 ELASTICITY AND ITS APPLICATION 27
28. 28. Price Elasticity and Total Revenue 0 Price elasticity Percentage change in Q = of demand Percentage change in P Revenue = P x Q If demand is elastic, then price elast. of demand > 1 % change in Q > % change in P The fall in revenue from lower Q is greater than the increase in revenue from higher P, so revenue falls.CHAPTER 5 ELASTICITY AND ITS APPLICATION 28
29. 29. Price Elasticity and Total Revenue 0Elastic demand increased Demand for(elasticity = 1.8) P revenue due your websites lost to higher P revenueIf P = \$200, due toQ = 12 and \$250 lower Qrevenue = \$2400. \$200If P = \$250, DQ = 8 andrevenue = \$2000.When D is elastic, Q 8 12a price increasecauses revenue to fall.CHAPTER 5 ELASTICITY AND ITS APPLICATION 29
30. 30. Price Elasticity and Total Revenue 0 Price elasticity Percentage change in Q = of demand Percentage change in P Revenue = P x Q If demand is inelastic, then price elast. of demand < 1 % change in Q < % change in P The fall in revenue from lower Q is smaller than the increase in revenue from higher P, so revenue rises. In our example, suppose that Q only falls to 10 (instead of 8) when you raise your price to \$250.CHAPTER 5 ELASTICITY AND ITS APPLICATION 30
31. 31. Price Elasticity and Total Revenue 0Now, demand is increased Demand forinelastic: revenue websites your due elasticity = 0.82 P to higher P lostIf P = \$200, revenue due toQ = 12 and \$250 lower Qrevenue = \$2400. \$200If P = \$250,Q = 10 and Drevenue = \$2500.When D is inelastic, Qa price increase 10 12causes revenue to rise.CHAPTER 5 ELASTICITY AND ITS APPLICATION 31
32. 32. A C T I V E L E A R N I N G 2:Elasticity and expenditure/revenueA. 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? 32
33. 33. A C T I V E L E A R N I N G 2:AnswersA. 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. 33
34. 34. A C T I V E L E A R N I N G 2:AnswersB. As a result of a fare war, the price of a luxury cruise falls 20%. Does luxury cruise companies’ total revenue rise or fall? Revenue = P x Q The fall in P reduces revenue, but Q increases, which increases revenue. Which effect is bigger? Since demand is elastic, Q will increase more than 20%, so revenue rises. 34
35. 35. APPLICATION: Does Drug Interdiction 0Increase 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.CHAPTER 5 ELASTICITY AND ITS APPLICATION 35
36. 36. Policy 1: Interdiction 0Interdiction new value of drug-reduces Price of related crimethe supply Drugs S2 D1of drugs. S1Since demand P2for drugs isinelastic, initial value P1P rises propor- of drug-tionally more relatedthan Q falls. crimeResult: an increase in Q2 Q 1 Quantitytotal spending on drugs, of Drugsand in drug-related crimeCHAPTER 5 ELASTICITY AND ITS APPLICATION 36
37. 37. Policy 2: Education 0 new value of drug-Education Price of related crimereduces the Drugsdemand for D2 D1drugs. S P and Q fall. P1 initial value Result: of drug- A decrease in P2 related total spending crime on drugs, and in drug-related Q2 Q 1 Quantity crime. of DrugsCHAPTER 5 ELASTICITY AND ITS APPLICATION 37
38. 38. 0 Price Elasticity of Supply Price elasticity Percentage change in Qs = of supply Percentage change in P Price elasticity of supply measures how much Qs responds to a change in P. Loosely speaking, it measures the price- sensitivity of sellers’ supply. Again, use the midpoint method to compute the percentage changes.CHAPTER 5 ELASTICITY AND ITS APPLICATION 38
39. 39. 0 Price Elasticity of Supply Price elasticity Percentage change in Qs = of supply Percentage change in P P Example: S P rises Price P2 by 8% elasticity P1 of supply equals Q 16% Q1 Q2 = 2.0 8% Q rises by 16%CHAPTER 5 ELASTICITY AND ITS APPLICATION 39
40. 40. 0 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. The steeper the curve, the smaller the elasticity. The next 5 slides present the different classifications, from least to most elastic.CHAPTER 5 ELASTICITY AND ITS APPLICATION 40
41. 41. 0“Perfectly inelastic” (one extreme) Price elasticity % change in Q 0% = = =0 % change in P 10% of supplyS curve: P S vertical P2Sellers’price sensitivity: P1 0 P rises QElasticity: by 10% Q1 0 Q changes by 0%CHAPTER 5 ELASTICITY AND ITS APPLICATION 41
42. 42. 0“Inelastic” Price elasticity % change in Q < 10% = = <1 % change in P 10% of supplyS curve: P S relatively steep P2Sellers’price sensitivity: P1 relatively low P rises QElasticity: by 10% Q1 Q2 <1 Q rises less than 10%CHAPTER 5 ELASTICITY AND ITS APPLICATION 42
43. 43. 0“Unit elastic” Price elasticity % change in Q 10% = = =1 % change in P 10% of supplyS curve: P intermediate slope S P2Sellers’price sensitivity: P1 intermediate P rises QElasticity: by 10% Q1 Q2 =1 Q rises by 10%CHAPTER 5 ELASTICITY AND ITS APPLICATION 43
44. 44. 0“Elastic” Price elasticity % change in Q > 10% = = >1 % change in P 10% of supplyS curve: P relatively flat S P2Sellers’price sensitivity: P1 relatively high P rises QElasticity: by 10% Q1 Q2 >1 Q rises more than 10%CHAPTER 5 ELASTICITY AND ITS APPLICATION 44
45. 45. 0“Perfectly elastic” (the other extreme) Price elasticity % change in Q any % = = = infinity % change in P 0% of supplyS curve: P horizontal P2 = P1 SSellers’price sensitivity: extreme P changes QElasticity: by 0% Q1 Q2 infinity Q changes by any %CHAPTER 5 ELASTICITY AND ITS APPLICATION 45
46. 46. 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.CHAPTER 5 ELASTICITY AND ITS APPLICATION 46
47. 47. 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, Qd doubles). For which product will P change the most? For which product will Q change the most? 47
48. 48. A C T I V E L E A R N I N G 3:Answers Beachfront property When supply (inelastic supply): is inelastic, P an increase in demand has a D1 D2 S bigger impact on price than P2 B on quantity. P1 A Q Q1 Q2 48
49. 49. A C T I V E L E A R N I N G 3:Answers New cars When supply (elastic supply): is elastic, P an increase in demand has a D1 D2 bigger impact S on quantity than on price. B P2 A P1 Q Q1 Q2 49
50. 50. How the Price Elasticity of Supply Can Vary 0 P Supply often S elasticity becomes \$15 <1 less elastic as Q rises, 12 due to elasticity capacity >1 limits. 4\$3 Q 100 200 500 525 CHAPTER 5 ELASTICITY AND ITS APPLICATION 50
51. 51. Other Elasticities The income elasticity of demand measures the response of Qd to a change in consumer income. Income elasticity Percent change in Qd = of demand 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.CHAPTER 5 ELASTICITY AND ITS APPLICATION 51
52. 52. Other Elasticities The cross-price elasticity of demand measures the response of demand for one good to changes in the price of another good.Cross-price elast. % change in Qd for good 1 = of demand % change in price of good 2 For substitutes, cross-price elasticity > 0 E.g., an increase in price of beef causes an increase in demand for chicken. For complements, cross-price elasticity < 0 E.g., an increase in price of computers causes decrease in demand for software.CHAPTER 5 ELASTICITY AND ITS APPLICATION 52
53. 53. CHAPTER SUMMARY  Elasticity measures the responsiveness of Qd or Qs to one of its determinants.  Price elasticity of demand equals percentage change Qd 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. CHAPTER 5 ELASTICITY AND ITS APPLICATION 53
54. 54. 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 equals percentage change in Qs divided by percentage change in P. When it’s less than one, supply is “inelastic.” When greater than one, supply is “elastic.”  Price elasticity of supply is greater in the long run than in the short run. CHAPTER 5 ELASTICITY AND ITS APPLICATION 54
55. 55. CHAPTER SUMMARY  The income elasticity of demand measures how much quantity demanded responds to changes in buyers’ incomes.  The cross-price elasticity of demand measures how much demand for one good responds to changes in the price of another good. CHAPTER 5 ELASTICITY AND ITS APPLICATION 55