It is a constraint that the principal has to take into consideration when offering contracts to the agent whose action is unobservable.
The meaning behind the constraint is simply that the principal will offer bundles of payment that induce the agent to do what the principal wants him to do, i.e., the net payoff for the preferable action is higher.   
 [此贴子已经被作者于2009-3-15 19:07:00编辑过]