Established gambling operators have argued that person-to-person wagering on Internet 'betting exchanges' represents unfair competition. In this paper we suggest that, in fact, betting exchanges have brought about significant efficiency gains by lowering transaction costs for consumers. We test this hypothesis using matched data on UK horse racing from betting exchanges and from traditional betting media. In contrast to traditional betting media, we find that betting exchanges exhibit both weak and strong form market efficiency.Further, we find evidence that an information based model explains the well documented favourite-longshot bias more convincingly than traditional explanations based on risk preferences.

The concept of information efficiency is central to many studies of financial markets, and these studies have been well surveyed to date. A betting market is an example of a simple financial market, but one which offers researchers the added advantage that it is characterized by a well-defined termination point at which each asset (or bet) possesses a definite value. In consequence, it is much more convenient to use this particular context to formulate tests of information efficiency, and from these tests to draw useful conclusions. This paper surveys the rapidly growing literature which has to date addressed this issue of information efficiency in betting markets.

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In this paper we test the hypothesis that bookmakers display superior skills to bettors in predicting the outcome of sporting events by using matched data from traditional bookmaking and person-to-person exchanges. Employing a conditional logistic regression model on horse racing data from the UK we find that, in high liquidity betting markets, betting exchange odds have more predictive value than the corresponding bookmaker odds.To control for potential spillovers between the two markets, we repeat the analysis for cases where prices diverge significantly. Once again, exchange odds yield more valuable information concerning race outcomes than the bookmaker equivalents.

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