Nearly $8.5 billion will be wagered on the NCAA Men’s Basketball Tournament that begins this week, according to a study , which was commissioned by the American Gaming Association and released Monday.

As many as 47 million people will gamble on March Madness in some way, according to the study.

Of those, 40 million people will wager an estimated $4.6 billion on the tournament by filling out 149 million collective brackets, 18 million people will wager $3.9 billion at a “sportsbook, online, with a bookie or with a friend.”

March Madness Most Popular U.S. Sports Betting Event

The total amount wagered makes the tournament the most lucrative sports betting event in the United States.

AGA, the leading national trade group representing the U.S. casino industry, commissioned global survey company Morning Consult to conduct the study. Morning Consult compiled the study by polling 11,000 people during the first week of March.

According to the study, bettors will participate in college basketball betting both legally and illegally in March.

Of the 18 million people who will wager, 4.1 million are expected to do so at either a casino sportsbook or via a legal app, 2.4 million will wager using a bookie, and 5.2 million will wager online – many using illegal offshore betting sites.

AGA Not Focused on Illegal Office Pools

Office pools where participants fill out a bracket are illegal in most states, but the AGA does not focus on stopping this form of gambling. The AGA instead is focused on curbing bettors from placing a March Madness wager via bookies or illegal offshore sportsbooks.

“We're not looking to be the fun police. That’s not our objective,” AGA senior vice president of public affairs Sara Slane said. “Clearly, people enjoy betting on the bracket and doing office pools. I think the larger point just goes to the fact that a couple of things.

“No. 1, this is such a massive part of our culture. People enjoy betting on sports and I think that's why you've seen such a wide range of acceptance throughout the United States to see legalized sports betting.

“And then secondarily, it highlights the fact that, yes, while it may be illegal, there is the opportunity now to make it legal and to regulate it and to recapture that revenue.”

First March Madness Post-PASPA

This March Madness is the first since May’s U.S. Supreme Court decision to overturn the Professional and Amateur Sports Protection Act of 1992. That ruling struck down a federal ban on legal sports betting outside of Nevada.

Since then several states passed legislation authorizing legalized sports betting. Delaware, Mississippi, New Jersey, New Mexico, Pennsylvania, Rhode Island, and West Virginia have since opened operational sportsbooks.

Collectively, $5.9 billion has been wagered in those seven states in the 10 months since the Supreme Court repealed PASPA.

Gaming industry analysts anticipate that will boon will continue, a belief supported by the AGA’s study on betting related to March Madness. A record $305.5 million was wagered in Nevada on the NCAA tournament last year.

“During this year’s tournament -- the first in post-PASPA America -- sports fans are expected to bet 40 percent more than they did on this year’s Super Bowl,” AGA CEO Bill Miller said in a statement.