Tetlock reasons that “our expectations of the future are derived from our mental models of how the world works, and every event is an opportunity to learn and improve those models” (251). However, as noted in previous chapters, it’s possible to improve these predictive models only by receiving clear feedback. Forecasting must therefore involve measuring and revising. To improve, forecasters must apply the same evidence-based guidelines used in medical testing.

However, the authors acknowledge that politicians and others in positions of power have a vested interest in keeping forecasting inaccurate. This is because accuracy is far from the only goal of forecasting: Political parties favor polls that make them look good and point to their victories, while campaigners use forecasts to rally their troops, sometimes exaggerating facts and figures in the service of their cause.

Tetlock and Gardner state that the future of forecasting will ultimately depend upon what people demand from it. Tetlock draws attention to early-20th-century doctor Ernest Amory Codman, who demanded better hospital evaluation; many in the medical establishment were as opposed to Codman’s demand as they now are to implementing systems of feedback in forecasting. However, the ultimate success of Codman’s methods inspired evidence-based testing even in nonmedical fields.