While economists designing plans may worry about ex ante welfare costs, public or private plan administrators may also worry about ex post regret - the after-the-fact costs of a decision.

• 经济学家在制订退休金计划时，事先福利成本是个难以解决的问题。而对公众或私人计划的管理人来说，他们所要操心的还有后悔成本，即在知道结果后的成本。