The politics of prediction

Forecasts have been fundamental to mankind’s journey from a small tribe on the African savannah to a species that can sling objects across the solar system with extreme precision. In physics we have developed models that are extremely accurate across vastly different scales from the sub-atomic to the visible universe. In politics we have bumbled along making the same sort of errors repeatedly.

Until the 20th century, medicine was more like politics than physics. Its forecasts were often bogus and its record grim. In the 1920s, statisticians invaded medicine and devised randomised controlled trials. Doctors, hating the challenge to their prestige, resisted but lost. Evidence-based medicine became routine and saved millions of lives. A similar battle has begun in politics. The result could be even more dramatic.

In 1984, Philip Tetlock, a political scientist, did something new — he considered how to assess the accuracy of political forecasts in a scientific way.