Planning fallacy
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The planning fallacy is the tendency to underestimate task-completion times. Real-life examples in public policy may include the construction of the Sydney Opera House and the Big Dig, both of which ran many years past their planned schedule.
In one study, 37 students were asked to estimate the completion times for their senior theses. The average estimate was 33.9 days. Only about 30% of the students were able to complete their thesis in the amount of time they predicted, and the average actual completion time was 55.5 days.
Some have attempted to explain the planning fallacy in terms of impression management theory.
One explanation, focalism, may account for the mental discounting of off-project risks. People formulating the plan may eliminate factors they perceive to lie outside the specifics of the project. Additionally, they may discount multiple improbable high-impact risks because each one is so unlikely to happen.
More prosaically, planners tend to focus on the project and underestimate time for sickness, vacation, meetings, and other "overhead" tasks. Planners also tend not to plan projects to a detail level that allows estimation of individual tasks, like placing one brick in one wall; this enhances optimism bias and prohibits use of actual metrics, like timing the placing of a average brick and multiplying by the number of bricks.
Compare to procrastination and optimism bias.
[edit] See also
[edit] References
- Buehler, R., Griffin, D., & Ross, M. (1994). Exploring the "planning fallacy": Why people underestimate their task completion times. Journal of Personality and Social Psychology, 67, 366-381.
- Buehler, R., Griffin, D., & Ross, M. (2002). Inside the planning fallacy: The causes and consequences of optimistic time predictions. In T. Gilovich, D. Griffin, & D. Kahneman (Eds.), Heuristics and biases: The psychology of intuitive judgment, 250-270. Cambridge, UK: Cambridge University Press.
[edit] External links
- If you don't want to be late, enumerate: Unpacking reduces the planning fallacy by Justin Kruger and Matt Evans
