The rapid legalization and spread of on-demand online sports betting have been damaging for athletes, fans, and anyone caught up in the craze that is fueling a multibillion-dollar industry.

Having sports gambling readily available on smartphones, easily connected to people’s bank accounts, has made it far easier than ever before for bettors to fall into addiction. Southern Methodist University examined 700,000 sports gamblers and found that less than 5% of them withdrew more money from their betting apps than they deposited into them. That 5% won more than $100 million, which was covered by bets placed by 80% of bettors. The bottom 3% of bettors lost enough money to make up half of the net revenue of their betting apps.