Economics 100 Lecture 8 Elasticity
Elasticity Price elasticity of demand Calculating the price elasticity of demand
Price Elasticity of Demand A measure of the responsiveness of the quantity demanded to price holding other things constant
Price Elasticity of Demand Figure 5.1 (a) shows the case in which a cut in supply increases total revenue
Price Elasticity of Demand Figure 5.1 (b) shows the case in which that same cut in supply decreases total revenue
Price Elasticity of Demand Whether total revenue increases or decreases with a price change depends on how sensitive the quantity demanded is to a change in price We would like to derive a measure of that sensitivity...
Price Elasticity of Demand The slope of a demand curve is a measure of the responsiveness of the quantity demanded of a good to a change in its price, holding constant all other influences on the quantity demanded Problem: slope depends on units of measurement!!!!!!!!!! (we cannot compare the demand for pizza and the demand for books!!!)
Price Elasticity of Demand Solution: Price elasticity of demand The price elasticity of demand is the percentage change in the quantity demanded of a good divided by the percentage change in its price Elasticity does not depend on units of measurement!!!
Calculating the Price Elasticity of Demand % Q % P
Note for ECON 100 IN ECON 100 we will calculate percentages of the average price and average quantity to avoid different numbers for a price rise and price fall This means that we really calculate the elasticity at a point midway between the equilibrium point before and after the price change. Ideally, we would want to calculate it at a single point, with no approximations…
% Q Q/ Q ave = % P P/ P ave
Calculating the Price Elasticity of Demand
Negative sign Price increase (a positive change in price) leads to a Quantity decrease (a negative change in quantity) The formula uses the absolute value of these changes and does not attach the minus sign to the decrease in quantity
ELASTICITY Note that the price-elasticity of demand is UNIT-FREE!!!, which is very useful for comparisons! Between countries between goods over time
Next, more about elasticities