Automated Market Makers Avoid Common Trader Mistakes and Information Redundancy: Research studies have shown that Iowa Electronic Marketplaces (IEM) merchants often violate the "law of one price." Consider betting on which of the two candidates will win. Logically, a bet that candidate A wins the election is equivalent to a bet that candidate B wins. However, in traditional double auctions, the prices of these contracts can diverge and, in addition, the IEM administrators observed that many traders take positions in the worst irrational contract. In contrast, automated market makers enforce the equality of logically equivalent bets.