Distinguish cognitive optimism bias from strategic misrepresentation

Recognize that some forecast inflation is genuine bias and some is deliberate spin — they require different fixes.

Why it works

Flyvbjerg identified two sources of forecast error: optimism bias (genuine cognitive distortion) and strategic misrepresentation (deliberate underestimation to win approval or funding). Reference class forecasting corrects optimism bias. Strategic misrepresentation requires institutional accountability mechanisms, not cognitive tools. Conflating the two leads to applying the wrong intervention.

How to do it

1. When reviewing a forecast, ask: "Does the forecaster have incentives to be optimistic for external reasons (funding, approval)?"
2. If yes, the estimate may be strategically low and should be further discounted beyond base-rate adjustment.
3. For your own forecasts, ask: "Am I optimistic because I genuinely believe it, or because I need others to approve this?"
4. Build in accountability: commit to tracking outcomes against forecasts and reporting the results.

Evidence

Flyvbjerg found evidence of both bias types in infrastructure project data, with strategic misrepresentation particularly prevalent in politically sensitive projects. The distinction is important because the remedy differs: cognitive debiasing tools vs. incentive structure reform. (observational)

Distinguishing the two sources from the outside is difficult — both produce the same observable pattern of forecast inflation. The categorization often requires knowing the forecaster’s situation.

Sources

• Flyvbjerg, Holm & Buhl (2002), "Underestimating costs in public works projects"
• Flyvbjerg (2008), "Curbing optimism bias and strategic misrepresentation"

Common mistake

Assuming all forecast errors are cognitive bias and responding only with debiasing training, while leaving the incentive structures that produce strategic misrepresentation intact.