How likely is it that humanity will go extinct by 2100? Which is more dangerous, AI or nuclear war? How successful will we be at developing alternative energy sources? Will we be able to control emerging pandemics? 

In the Existential Risk Persuasion Tournament (XPT), we asked 169 participants—including accurate forecasters and experts on existential risks—to help us understand how people make forecasts about questions like these. We incentivized them to talk to each other, explain their reasoning, and update their forecasts, working individually and in teams to come up with high-quality forecasts and rationales about the risks humanity faces in the next century. 

We discovered points where our participants agree and disagree on what they expect to happen to humanity in the coming decades, on topics related to AI, nuclear war, biological pathogens, and other dangers. We were also left with some puzzling questions. Why are superforecasters (people who have been accurate about short-run forecasts in the past) so much less worried about catastrophic outcomes than experts, even though they agree on many other questions? Why didn’t they get more worried when they heard the experts explaining their positions? The XPT is a first step toward understanding how expert knowledge and forecasting skill are related, and how people do (or don’t) learn from one another when they make forecasts about important long-term questions.