Social Learning, Strategic Incentives and Collective Wisdom: An Analysis of the Blue Chip Forecasting Group J. Peter Ferderer Department of Economics Macalester College St. Paul, MN 55105
[email protected] Adam Freedman Chicago, IL 60601
[email protected] July 22, 2015 ABSTRACT: Using GDP growth forecasts from the Blue Chip survey between 1977 and 2011, we measure absolute consensus errors and forecast dispersion for each of the 24 monthly forecast horizons and provide three main findings. First, the size of consensus errors and forecast dispersion are negatively correlated over longer-term forecast horizons (from 24 to 13 months). This finding is consistent with the hypothesis that the Lawrence Klein forecasting award, which is based on performance of 12-month-head forecasts, increased the group’s collective wisdom by raising the incentive to anti-herd. Second, absolute consensus errors and forecast dispersion display significant negative temporal variation for the longest horizons (24 to 20 months). Third, after the early 1990s (i) there was a dramatic decline in forecast dispersion associated with a significant increase in the size of longer-term consensus errors, and (ii) forecasts bracket realized GDP growth much less frequently. The final two results suggest that increased herding or reduced model diversity caused collective wisdom to diminish in the second part of the sample. JEL Classifications: E37 Forecasting and Simulation: Models and Applications D70 Analysis of Collective Decision-Making, General D83 Search; Learning; Information and Knowledge; Communication; Belief Keywords: social learning, herding, strategic incentives, reputation, consensus forecasts, collective wisdom, forecast errors, forecast dispersion, Great Moderation 0 The key lesson I would draw from our experience is the danger of relying on a single tool, methodology or paradigm.