demand in this case is therefore zero, and the demand curve is said to be perfectly inelastic This is a theoretically extreme case, and no good that has been studied empirically exactly fits it A good that comes close, at least over a specific price range, is insulin A diabetic will not consume more insulin as its price falls but, over some price range, will consume the amount needed to control the disease Figure 5.5 Demand Curves with Constant Price Elasticities The demand curve in Panel (a) is perfectly inelastic The demand curve in Panel (b) is perfectly elastic Price elasticity of demand is −1.00 all along the demand curve in Panel (c), whereas it is −0.50 all along the demand curve in Panel (d) As illustrated in Figure 5.5 "Demand Curves with Constant Price Elasticities", several other types of demand curves have the same elasticity at every point on them The demand curve in Panel (b) is horizontal This Attributed to Libby Rittenberg and Timothy Tregarthen Saylor URL: http://www.saylor.org/books/ Saylor.org 247