Testing the Wisdom of Crowds in the field: Transfermarkt valuations and international soccer results

This paper investigates the value of collective judgments which stem from settings that have not been designed explicitly to elicit the 'Wisdom of Crowds'. In particular, I investigate information obtained from transfermarkt.de, an online platform where a crowd of registered users assess the value of professional soccer players. I show that forecasts of international soccer results based on the crowd's valuations are more accurate than those based on standard predictors, such as the FIFA ranking and the ELO rating. When this improvement in forecasting performance is applied to betting strategies, it leads to sizable monetary gains. I further exploit information on the preferences of individual crowd members in order to investigate whether wishful thinking hampers the accuracy of crowd valuations, but fail to find evidence that such is the case. (C) 2017 International Institute of Forecasters. Published by Elsevier B.V. All rights reserved.