is demand elasticity constant?
Constant Elasticity Demand Curves. The elasticity of demand is the same at every point along a constant elasticity demand curve. Panel a of the figure shows five constant elasticity demand curves. A perfectly inelastic demand curve, where e = 0 everywhere, is a vertical straight line. The next most vertical demand curve in the figure is also inelastic, with a demand elasticity of -1/3 everywhere.