Elasticities(弹性) ◆ Elasticity measures the“ sensitivity of one variable with respect to another o The elasticity of variable x with respect to variable y is △X X,y o△yElasticities （弹性） ◆Elasticity measures the “sensitivity” of one variable with respect to another. ◆The elasticity of variable X with respect to variable Y is  x y x y , % % = .  