The change in the probability of purchasing a given coffee variety as the price of one of the varieties changes is conveniently expressed in elasticity form. The own-price elasticity of 7T i at a given price Pi is given by jj.Pii 1 - TTj), and the cross-price elasticity for
It i as the price of another alternative Pj changes is -ปีb Pjijtj) (Ben-Akiva and Lerman 1985; Train 2003). This cross-price elasticity is the same for all i; that is, a change in the price of alternative j changes the probabilities of all other alternatives by the same percentage (Train 2003).