Planning Fallacy (Extended)

The extended model adds to Kahneman's planning fallacy by incorporating Flyvbjerg's finding that STRATEGIC MISREPRESENTATION (deliberate lying about project prospects) operates alongside genuine cognitive bias—and in many organizational contexts, the deliberate distortion is larger than the cognitive error. The extended model identifies three compounding sources of planning failure: (1) Cognitive optimism (genuine inside-view bias). (2) Political pressure (organizations reward optimistic projections). (3) Strategic misrepresentation (promoters deliberately distort to get approval). All three push in the same direction—toward underestimation—making the aggregate bias much larger than any single source.

When to use it

When project overruns persist despite improved estimation methods; when organizational culture rewards optimistic projections; when the pattern of cost overruns and benefit shortfalls is systematic rather than random; when designing approval processes that need to be resistant to all three sources of bias.

How it can help

Address all three sources simultaneously. For cognitive optimism: reference class forecasting and personal bias calibration. For political pressure: reward forecast accuracy rather than optimism in the approval process; create safe channels for realistic estimates. For strategic misrepresentation: independent cost estimation, contractual accountability for estimates, and penalties for systematic overruns. The extended model shows why 'better estimation training' alone doesn't fix project overruns—because much of the bias is institutional (political pressure) and deliberate (strategic misrepresentation), not merely cognitive.