| Summary: | This study analyzes the relative accuracy of experts, polls,
and the so-called ‘fundamentals’ in predicting the popular vote in the four
U.S. presidential elections from 2004 to 2016. Although the majority (62%) of
452 expert forecasts correctly predicted the directional error of polls, the
typical expert’s vote share forecast was 7% (of the error) less accurate than a
simple polling average from the same day. The results further suggest that
experts follow the polls and do not sufficiently harness information
incorporated in the fundamentals. Combining expert forecasts and polls with a
fundamentals-based reference class forecast reduced the error of experts and
polls by 24% and 19%, respectively. The findings demonstrate the benefits of
combining forecasts and the effectiveness of taking the outside view for
debiasing expert judgment.
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