Futarchy is a theoretical political system that utilizes betting markets to make decisions. It has not been implemented in any substantial way.
Futarchy works with conditional bets (i.e., if candidate-of-choice wins, the GDP will go up 10%+). People can bet for or against these estimations, such as that example, despite relying on conditionals (that the candidate will win). If the conditional is not met (the candidate loses), all bets on the question are nullified for all parties.
With a well-trained betting market, consisting of conditional bets, it is then theoretically possible to predict the outcomes of certain possibilities (which candidate is more likely to raise the GDP?) The political system could theoretically incorporate consideration of these determinations in an automated way.
The betting market is considered a good system for making predictions, because betters have skin in the game.