Suppose they have a written contract, or even an unwritten contract, what enforces the contract for colluding firms or crooks in jail?

假如他们签了一份书面协议,或干脆口头的,他们怎么强制履行呢

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A contract is more then communication, a contract is communication with teeth. It actually changes the payoffs.

协议的效力大于口头约定,协议是有违约责任的,它影响收益

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So basically, we're stuck with this verbal agreement and we both have an incentive to cheat and produce more whatever it is, sugar water.

但不管怎样,在这个口头协议不起作用,我们都有违约,生产更多这种糖水的动机

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