Americans will bet a total of $8.5 billion on the NCAA “March Madness” men’s basketballOpens a New Window. tournament this month, with one out of every five adults placing a wager on the eventOpens a New Window., according to new estimates from the American Gaming Association.

Roughly 47 million U.S. adults are expected to gamble on the event, according to the results of a survey conducted by the trade group. Of the $8.5 billion total, about $4.6 billion will be on the line for 149 million tournament brackets.

“During this year’s tournament – the first in post-PASPA America – sports fans are expected to bet 40% more than they did on this year’s Super Bowl,” Bill Miller, AGA’s president and chief executive officer, said in a statement. “Unlike any other sporting event in the country, March Madness attracts millions who fill out brackets, make casual bets with friends or wager at a legal sportsbook, which Americans can now do more than ever before.”

The NCAA tournament features the top 68 men’s basketball teams in the country. Of roughly 11,000 adults who participated in the AGA’s online survey, 29 percent said Duke would win the tournament, while 9 percent backed Gonzaga and 8 percent picked North Carolina.

The U.S. Supreme Court voted last year to strike down a longstanding federal ban on sports betting, enabling states to determine whether to implement gambling on a case-by-case basis. The eight states with legalized sports betting have taken more than $5.9 billion in bets since the court’s ruling last May.

However, many Americans are still placing bets on sports through illicit means. An estimated 2.4 million people will bet on the tournament using illegal bookies.