The average overall returns on online sports betting are negative and getting worse. The change in mix of online bets that gaming companies are promoting, specifically the parlay bet, has resulted in gamblers winning less, while gambling companies win more. Parlay bets, where gamblers bet on several games or variables within a contest in a single bet, have proliferated in online gambling. As parlay bets grow, gambling companies see a rise in hold rates, which is the percentage the house keeps after paying out a winning bet. Hold rates on parlay bets are significantly higher at around 15 to 25 percent, compared to the 5 percent hold rate for typical straight bets involving single contests.