>In a 1994 study, 37 psychology students were asked to estimate how long it would take to finish their senior theses. The average estimate was 33.9 days. They also estimated how long it would take "if everything went as well as it possibly could" (averaging 27.4 days) and "if everything went as poorly as it possibly could" (averaging 48.6 days). The average actual completion time was 55.5 days, with only about 30% of the students completing their thesis in the amount of time they predicted.
>Another study asked students to estimate when they would complete their personal academic projects. Specifically, the researchers asked for estimated times by which the students thought it was 50%, 75%, and 99% probable their personal projects would be done.
>13% of subjects finished their project by the time they had assigned a 50% probability level;
>19% finished by the time assigned a 75% probability level;
>45% finished by the time of their 99% probability level.
>A survey of Canadian tax payers, published in 1997, found that they mailed in their tax forms about a week later than they predicted. They had no misconceptions about their past record of getting forms mailed in, but expected that they would get it done more quickly next time. This illustrates a defining feature of the planning fallacy; that people recognize that their past predictions have been over-optimistic, while insisting that their current predictions are realistic.