Why projects overrun: the planning fallacy
Why does an experienced team keep underestimating deadlines, project after project? Decision psychology has named and measured the phenomenon.
The measured phenomenon
Roger Buehler, Dale Griffin and Michael Ross (1994, Journal of Personality and Social Psychology) show people predict over-optimistic completion times for their own tasks, even while recalling past predictions were wrong. Studies mostly involve students and individual tasks.
Inside and outside view
Daniel Kahneman and Dan Lovallo (1993, Management Science) contrast the 'inside view', focused on the project's scenario, with the 'outside view', based on outcomes of comparable projects. The article is conceptual.
The collective nuance
In teams, social pressure and the wish to convince a sponsor may amplify optimism, though group research is thinner than individual research. (our executive and employee training programmes)
The limit of common practice
Adding a flat buffer at the end treats the symptom without questioning the estimate; the buffer is often consumed or negotiated away.
A practical check in Zurich
Before fixing a deadline, find three comparable internal projects and their actual duration, then test the estimate against them. Tracking estimate-versus-actual over the year shows whether calibration improves. To go further: explore the Project Management training in Zurich, or browse our executive and employee training programmes in Switzerland.
In pictures: Project Management in Zurich
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