The Effectiveness of Peer Prediction in Long-Term Forecasting

In human forecasting, proper scoring rules are used to elicit effort in providing accurate probability forecasts of future events. A challenge, though, is that users do not receive feedback about their forecasts until the outcomes are realized. Nor is it clear whether these schemes are effective in motivating continual attention, and updating forecasts on difficult or dynamically changing problems, for which there is a continuous inflow of new information over time. Through a large-scale experiment on Amazon Mechanical Turk (MTurk), we investigate whether peer prediction methods can be used to complement methods of proper scoring rules, and improve engagement of users and ultimately the quality of forecasts. Peer prediction provides immediate feedback, by comparing one forecaster's prediction with that of another, this feedback provided as rank placement or through incentive payments. One of a very small number of experimental studies into peer prediction, ours is the first to test peer prediction in this hybrid role. We show that providing daily feedback through peer prediction has a significant effect in increasing engagement with the forecasting platform. Moreover, a hybrid scheme that combines scoring rules with peer prediction feedback (via rank feedback) is, together with the basic scoring rule method, generally the best for accuracy. Since the hybrid scheme also improves user engagement, this suggests that the hybrid scheme would provide the best accuracy for longer term forecasting events.