The basic form of economic exchange is a bilateral relationship between buyer and seller. If economic conditions are common knowledge there is no problem in principle to determine the efficient quantity to trade. But if benefits are known only to the buyer and costs are known only to the seller...

Tournaments, reward structures based on rank order, are compared with individual contracts in a model with one risk-neutral principal and many risk-averse agents. Each agents' output is a stochastic function of his effort level plus an additive shock term that is common to all the agents. The...