Users participate in an estimate contest and a prediction market for forecasting an outcome of a future event. Data from the estimate contest and the prediction market can be combined to obtain accurate information about overall group beliefs and individual or sub-groups beliefs. In the estimate contest, users provide estimated probabilities of occurrence for different possible outcomes of the event. Trades can be proposed, or automatically executed, based on differences between the user's estimated probabilities and probabilities obtained from a prediction market in which the user can buy and sell securities which represent the different outcomes. For example, a buying opportunity may be present when the user's estimated probability exceeds the prediction market's probability. Further, the user can express a risk level which is factored into the proposed trades.