We infer unobserved strategies from the actions of buyers in posted-offer market economics experiments, with a new application of a Bayesian technique. We find that buyer strategies are effective as a counteracting response to monopoly power: market prices and monopolist profits are negatively correlated with strategy complexity. One strategy is particulary effective: the unconditional and intense forgoing of profitable purchases early in the game is more effective than punishments that trigger when the price exceeds a threshhold. We conclude that strategy inference provides new insights into strategic behavior, and should at least complement existing methods of statistical analysis.