Separating insider and informed behavior: Evidence from a natural setting

Abstract

Previous literature has established the need to separate insider from expert trading in both financial and betting markets. This type of separation proves difficult to achieve because experts and insiders co‐exist in most market settings. Utilizing novel betting markets in which expert skill bettors are unable to use their expert knowledge, this study uncouples insider from expert betting, and allows more direct measurement of insider trading than in previous empirical tests. Evidence is presented in favor of some predictions from the highly cited Shin model of insider trading. Price setters charge an extra premium in markets with high proportions of insiders when compared to equivalent markets. The insiders accurately predict event outcomes, and their presence exacerbates a well known bias in betting market prices whereby returns on betting favorites is higher than for bets on longshots.