Why Everything Takes 2.71828... Times as Long as Expected
研究发现，在无时间约束时，无限步骤任务的实际耗时与预期耗时之比趋近于自然常数e（约2.71828），而时间约束只会让情况更糟，这挑战了经济学对预期形成的基本假设。
It is widely observed, and almost as widely lamented, that everything takes longer than one expects. However, most attempts to explain why deadlines are missed and budgets overrun go no farther than Murphy's (n.d.) often-quoted aphorism. Blaming the phenomenon on unrealistic expectations, as Handtvefer (1982) does, cannot explain why expectations are not revised after repeated disappointment. The problem presents both a theoretical challenge to economic science and an issue of great practical importance; a procedure for predicting delays could save a lot of money and frustration. In the absence of constraints on the time available for a job, it turns out that the ratio of time taken to time expected tends to e = 2.71828... for a job consisting of an infinite number of steps. Shorter jobs exceed the expected time by ratios less than e but never less than 2. Constraints on time, when the time available is less than what is expected to be needed for completion, only make matters worse.