Americans could bet $3.1 billion on NCAA men's basketball tournament, according to survey

Billions of dollars are expected to be wagered on the NCAA tournament, the most heavily bet sporting event in the United States.

According to research from the American Gaming Association (AGA) released Sunday, an estimated 45 million people could combine to wager $3.1 billion on the NCAA tournament through bracket pools and wagers with sportsbooks and friends. The $3.1 billion amount is approximately three times more than how much was estimated to have been bet on this year's Super Bowl with U.S. sportsbooks.

The AGA's estimates are based on a national survey of 2,201 adults conducted by the firm Morning Consult during the first week of March.

The amount of people planning to bet on the tournament is down slightly from last year's survey results, and the responses this year indicate a shift in how Americans will wager on March Madness.

"This year, Americans plan to place a greater share of their bets [on the tournament] through non-bracket," the American Gaming Association stated in a release announcing the survey results. "Of their total betting budget on this year's tournament. Americans expect to place 76 percent of their wagers outside of brackets, up from 55 percent last year."

Thirty states -- nine more than last year -- and the District of Columbia have launched legal betting markets. Approximately 29 million more American adults can legally wager in their home state compared to last year's NCAA tournament, potentially contributing to the shift in how people plan to bet on March Madness.

"There is no doubt this year will generate the highest legal [betting] handle in March Madness history," AGA president and CEO Bill Miller said in the release.

Gonzaga is the consensus favorite to win the NCAA tournament at sportsbooks and is by far the public's most popular pick. In the first four hours after the bracket was released, 34.5% of entries in the ESPN's Tournament Challenge contest had the Zags winning the championship.