ECONOMIC SECOND EDITION in MODULES S Paul Krugman Robin Wells with Margaret Ray and David Anderson MODULE 12 48 Other Elasticities Krugman Wells How the cross price elasticity of demand measures the responsiveness of demand for one good to changes in the price of another good The meaning and importance of the income elasticity of demand a measure of the responsiveness of demand to changes in income The significance of the price elasticity of supply which measures the responsiveness of the quantity supplied to changes in price The factors that influence the size of these various elasticities 3 of 16 Other Elasticities The cross price elasticity of demand between two goods measures the effect of the change in one good s price on the quantity demanded of the other good It is equal to the percent change in the quantity demanded of one good divided by the percent change in the other good s price The cross price elasticity of demand between Goods A and B 4 of 16 Cross Price Elasticity Goods are substitutes when the cross price elasticity of demand is positive Goods are complements when the cross price elasticity of demand is negative 5 of 16 The Income Elasticity of Demand The income elasticity of demand is the percent change in the quantity of a good demanded when a consumer s income changes divided by the percent change in the consumer s income 6 of 16 The Income Elasticity of Demand When the income elasticity of demand is positive the good is a normal good The quantity demanded at any given price increases as income increases When the income elasticity of demand is negative the good is an inferior good The quantity demanded at any given price decreases as income increases 7 of 16 Where Have All the Farmers Gone The income elasticity of demand for food is much less than 1 so it is income inelastic Competition among farmers means that technological progress leads to lower food prices Meanwhile the demand for food is price inelastic so falling prices of agricultural goods other things equal reduce the total revenue of farmers Progress in farming has been good for consumers but bad for farmers 8 of 16 The Price Elasticity of Supply The price elasticity of supply is a measure of the responsiveness of the quantity of a good supplied to the price of that good It is the ratio of the percent change in the quantity supplied to the percent change in the price as we move along the supply curve 9 of 16 Two Extreme Cases of Price Elasticity of Supply a Perfectly Inelastic Supply Price Elasticity of Supply 0 b Perfectly Elastic Supply Price Elasticity of Supply Price of cell phone frequency Price of pizza S 1 3 000 An increase in price 2 000 0 leaves the quantity supplied unchanged 100 At exactly 12 producers will produce any quantity At any price above 12 quantity supplied is infinite 12 S2 At any price below 12 quantity supplied is zero Quantity of cell phone frequencies 0 Quantity of pizzas 10 of 16 The Price Elasticity of Supply There is perfectly inelastic supply when the price elasticity of supply is zero so that changes in the price of the good have no effect on the quantity supplied A perfectly inelastic supply curve is a vertical line There is perfectly elastic supply when even a tiny increase or reduction in the price will lead to very large changes in the quantity supplied so that the price elasticity of supply is infinite A perfectly elastic supply curve is a horizontal line 11 of 16 What Factors Determine the Price Elasticity of Supply The Availability of Inputs The price elasticity of supply tends to be large when inputs are readily available and can be shifted into and out of production at a relatively low cost It tends to be small when inputs are difficult to obtain Time The price elasticity of supply tends to grow larger as producers have more time to respond to a price change This means that the long run price elasticity of supply is often higher than the short run elasticity 12 of 16 An Elasticity Menagerie 13 of 16 An Elasticity Menagerie 14 of 16 1 The cross price elasticity of demand measures the effect of a change in one good s price on the quantity of another good demanded 2 The income elasticity of demand is the percent change in the quantity of a good demanded when a consumer s income changes divided by the percent change in income 3 If the income elasticity is greater than 1 a good is income elastic if it is positive and less than 1 the good is income inelastic 4 The price elasticity of supply is the percent change in the quantity of a good supplied divided by the percent change in the price 15 of 16 5 If the quantity supplied does not change at all we have an instance of perfectly inelastic supply the supply curve is a vertical line 6 If the quantity supplied is zero below some price but infinite above that price we have an instance of perfectly elastic supply the supply curve is a horizontal line 7 The price elasticity of supply depends on the availability of resources to expand production and on time It is higher when inputs are available at relatively low cost and the longer the time elapsed since the price change 16 of 16