THE RELATIVE IMPORTANCE OF STRENGTH AND WEIGHT IN PROCESSING NEW INFORMATION IN THE COLLEGE FOOTBALL BETTING MARKET

Abstract

Griffin and Tversky (1992) suggest that individuals, when formulating posterior probabilities based on the available evidence, tend to overreact to a new piece of evidence’s strength while underreacting to the relative importance of its weight.  We test this prediction using the college football betting market, a market that is commonly employed in tests for efficiency and rationality.  Using average points in excess of the spread and streak against the spread as measures for strength and weight, respectively, we find that bettors overreact to strength and underreact to weight.  These results are consistent with the predictions of Griffin and Tversky, as well as with the findings of Sorescu and Subrahmanyam (2006) and Barberis, Shleifer, and Vishny (1998) in financial market settings.  Our work also provides insight into how behavioral biases might affect price-formation processes in other markets.The authors thank Tod Perry, Omar Shehryar, and Kumar Venkataraman for their careful feedback and thoughtful suggestions.  The authors are also grateful for comments from seminar participants at the 2008 Midwest Finance Association meetings in San Antonio and 2008 Southwestern Finance Association meetings in Houston, as well as from seminar participants at Montana State University.  (The authors are responsible for any outstanding errors in this paper.)