The authors interpret historical evidence in light of a repeated-game model to conclude that merchant guilds emerged during the late medieval period to allow rulers of trade centers to commit to the security of alien merchants. The merchant guild developed the theoretically required attributes,...

Consider a family of maximization models in which the optimum trades off beneficial and costly effects. Then comparative statics derived under many kinds of simplifying assumptions about the benefits technology are also true for general (convex and nonconvex) technologies. For example, any...