In this paper, a survey is undertaken of studies that examines the extent to which systematic patterns of behaviour in betting markets can generate above-average
or even abnormal returns, the latter being most conveniently defined for these
purposes as a profit. The paper concludes that although betting markets do tend
to process efficiently the information available to them, there are clear
opportunities to earn above-average returns. Moreover, there is significant
evidence that some bettors are able to profit by withholding and subsequently
utilising superior information.