2ElasticityA measure of the responsiveness of one variable (usually quantity demanded or supplied) to a change in another variableMost commonly used elasticity: price elasticity of demand, defined as:Price elasticity of demand =
3Price elasticity of demand Demand is said to be:elastic when Ed > 1,unit elastic when Ed = 1, andinelastic when Ed < 1.
6Elasticity & slopea price increase from $1 to $2 represents a 100% increase in price,a price increase from $2 to $3 represents a 50% increase in price,a price increase from $3 to $4 represents a 33% increase in price, anda price increase from $10 to $11 represents a 10% increase in price.Notice that, even though the price increases by $1 in each case, the percentage change in price becomes smaller when the starting value is larger.
10ExampleSuppose that quantity demanded falls from 60 to 40 when the price rises from $3 to $5. The arc elasticity measure is given by:In this interval, demand is inelastic (since elasticity < 1).
11Elasticity and total revenue Total revenue = price x quantityWhat happens to total revenue if the price rises?Price elasticity of demand =
12Elasticity and TR (cont.) Price elasticity of demand =A reduction in price will lead to:an increase in TR when demand is elastic.a decrease in TR when demand is inelastic.an unchanged level of total revenue when demand is unit elastic.
13Elasticity and TR (cont.) Price elasticity of demand =In a similar manner, an increase in price will lead to:a decrease in TR when demand is elastic.an increase in TR when demand is inelastic.an unchanged level of total revenue when demand is unit elastic.
15Price discriminationdifferent customers are charged different prices for the same product, due to differences in price elasticity of demandhigher prices for those customers who have the most inelastic demandlower prices for those customers who have a more elastic demand.
16Price discrimination (cont.) customers who are willing to pay the highest prices are charged a high price, andcustomers who are more sensitive to price differentials are charged a low price.
17Determinants of price elasticity Price elasticity is relatively high when:close substitutes are available,the good or service is a large share of the consumer's budget, anda longer time period is considered.
18Cross-price elasticity of demand The cross-price elasticity of demand between two goods j and k is defined as:
19Cross-price elasticity (cont.) cross-price elasticity is positive if and only if the goods are substitutescross-price elasticity is negative if and only if the goods are complements.
20Income elasticity of demand A good is a normal good if income elasticity > 0.A good is an inferior good if income elasticity < 0.
21Income elasticity of demand A good is a luxury good if income elasticity > 1.A good is a necessity good if income elasticity < 1.
25Determinants of supply elasticity short run - period of time in which capital is fixedall inputs are variable in the long runsupply will be more elastic in the long run than in the short run since firms can expand or contract their capital in the long run.
26Tax incidencedistribution of the burden of a tax depends on the elasticities of demand and supply.When supply is more elastic than demand, consumers bear a larger share of the tax burden.Producers bear a larger share of the burden of a tax when demand is more elastic than supply.