For those who don’t know yet about Intrade.com let me introduce this website. Intrade.com is what we could call the stock exchange of political issues. Well, in fact they include not only political issues but also related to weather, current events, foreign affaires,… They define it as:
is a prediction market. What is a prediction market? It's a market that allows you to make predictions on the outcome of hundreds of real-world events. Stock exchanges find the price of stocks, and futures markets find the price of commodities. Prediction markets find the probability of something happening - a predefined, uncertain future event.