Identifying Confirmatory Bias in the Field: Evidence from a Poll of Experts

56 Pages Posted: 12 May 2012 Last revised: 30 May 2012

See all articles by Rodney Andrews

Rodney Andrews

University of Texas at Dallas

Trevon Logan

Ohio State University; National Bureau of Economic Research (NBER)

Michael Sinkey

affiliation not provided to SSRN

Date Written: May 2012

Abstract

Laboratory experiments have established the existence of cognitive biases, but their explanatory power in real-world economic settings has been difficult to measure. We estimate the extent of a cognitive bias, confirmatory bias, among experts in a real-world environment. In the Associated Press Top 25 College Football Poll expert pollsters are tasked with assessing team quality, and their beliefs are treated week-to-week with game results that serve as signals about an individual team's quality. We exploit the variation provided by actual game results relative to market expectations to develop a novel regression-discontinuity approach to identify confirmatory bias in this real-world setting. We construct a unique personally-assembled dataset that matches more than twenty years of individual game characteristics to poll results and betting market information, and show that teams that slightly exceed and barely miss market expectations are exchangeable. The likelihood of winning the game, the average number of points scored by teams and their opponents, and even the average week of the season are no different between teams that slightly exceed and barely miss market expectations. Pollsters, however, significantly upgrade their beliefs about a team's quality when a team slightly exceeds market expectations. The effects are sizeable-- nearly half of the voters in the poll rank a team one slot higher when they slightly exceed market expectations; one-fifth of the standard deviation in poll points in a given week can be attributed to confirmatory bias. This type of updating suggests that even when informed agents make repeated decisions they may act in a manner which is consistent with confirmatory bias.

Suggested Citation

Andrews, Rodney and Logan, Trevon and Sinkey, Michael, Identifying Confirmatory Bias in the Field: Evidence from a Poll of Experts (May 2012). NBER Working Paper No. w18064. Available at SSRN: https://ssrn.com/abstract=2056692

Rodney Andrews (Contact Author)

University of Texas at Dallas ( email )

Trevon Logan

Ohio State University ( email )

2100 Neil Avenue
Columbus, OH OH 43210
United States

National Bureau of Economic Research (NBER)

1050 Massachusetts Avenue
Cambridge, MA 02138
United States

Michael Sinkey

affiliation not provided to SSRN ( email )

No Address Available

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