“…In most of researches related to flexible supply contracts, for instance Wang et al (2006), Donohue (2000), and BarnesSchuster et al (2002), measuring whether one's performance is improved or not depends on whether the expected profit at the beginning of the whole planning horizon can be increased or not. That is, if a proposed model increases expected profit at the beginning of the whole planning horizon, one can say that the proposed model improves the performance, and vice versa.…”