Superforecasting: The Art and Science of Prediction

by Philip E. Tetlock

David Rogg, a superforecaster and semiretired software engineer living in Virginia, did that when he tackled a question about terrorism in Europe. It was early 2015, shortly after terrorists had murdered eleven people at the Paris satirical magazine Charlie Hebdo. IARPA asked: “Will there be an attack carried out by Islamist militants in France, the UK, Germany, the Netherlands, Denmark, Spain, Portugal, or Italy between 21 January and 31 March 2015?” At a moment when the media was awash with information about Islamist terrorism and Muslim communities in Europe, it was tempting to rush to the inside view. David knew better. First, he found a list of Islamist terror attacks on Wikipedia. Then he counted the number of attacks in the specified countries over the previous five years. There were six. “So I calculate the base rate as 1.2/year,” he wrote in the GJP forum.