. >> this is my fantasy basebal b. john: you can play if, say, you think trump is more likely than this to become president, place a bet. if he wins, you make about five bucks for every dollar you bet. >> yeah. i'm actually doing pretty well. maybe tripled or quadrupled what i put in. >> it literally pays to be right. john: it turns out competitive prediction markets like this are much more accurate than polls. >> consistently, test after test, the markets forecasted elections more accurately than polls. john: in november, ben carson surged to first place in polls but the bettors knew better. the odds had him at just 9%. now he's below 1%. in 2012 when these candidates surged to fist place in polls, the prediction markets correctively said, no, romney will win. it also correctly predicted results in almost every state. in 2012, every state but one. >> the market is consistently as accurate or more accurate than the other. you can take that to the bank. john: bets on the prediction market in trade even predicted when saddam