A recent scandal involving a Green Beret who was arrested for betting on a classified US raid has highlighted the potential risks of insider trading in prediction markets. However, a new study suggests that this incident may be more than just an isolated case.
The research, conducted by a team of academics from the London Business School and Yale, analyzed over 1.7 million accounts and $13.7 billion in trading volume on the Polymarket platform, and found that just 3% of traders are responsible for the majority of price discovery. These traders consistently demonstrate a high level of accuracy in their predictions, and their activity serves to drive prices towards the correct outcome.
In contrast, the remaining 97% of traders tend to lose money, providing liquidity and generating volume, but ultimately being on the wrong side of trades. The study's findings challenge the conventional wisdom that prediction markets work due to the collective knowledge of their participants, and instead suggest that it is the informed minority that drives market accuracy.
The researchers used a novel approach to distinguish between skill and luck, rerunning each trader's bets 10,000 times with the direction of the bet randomized. This allowed them to establish a benchmark for what each trader's profits would look like in the absence of any real edge. The results showed that among the biggest winners, only 12% were able to consistently beat the benchmark, while many apparent winners were found to be merely lucky. The study also found that the activity of skilled traders serves to improve market accuracy, particularly in the final stages before an event is resolved.
Furthermore, these traders are often the first to react to new information, adjusting their positions in response to events such as Federal Reserve announcements or corporate earnings reports. However, the same edge that makes skilled traders valuable to price discovery also raises concerns about the potential for insider trading. The study highlights the risk of insider trading in a concrete case, involving the US removal of Nicolás Maduro from power in Venezuela. In the days leading up to the event, three newly created accounts on Polymarket placed large bets on the outcome, with the price moving in their favor shortly after.
The accounts collectively made over $630,000, and two of them stopped trading entirely soon after. While there is no evidence of wrongdoing in this case, the incident serves to illustrate the potential risks of insider trading in prediction markets. Overall, the study's findings suggest that prediction markets work due to the presence of a small group of informed traders, rather than the collective knowledge of the crowd.