The $9 billion is more than double what the AGA estimated was bet on the Super Bowl ($3.9 billion) in the United States. The total number of brackets expected to be filled out will be greater than the number of ballots cast (nearly 66 million) for President Barack Obama in the 2012 election.
The AGA projects that 40 million Americans will fill out at least one bracket, with the majority filling out two. The average bet per bracket is $29, with $2 billion projected to be wagered in pools across the nation.
The poll, conducted by GfK Custom Research North America, consisted of 1,000 completed interviews of an approximately equal number of male and female adults.
"Sports betting has played a major role in making March Madness the big-time event it is today," Geoff Freeman, president and CEO of the AGA, said in a statement. "With more people filling out brackets than casting a ballot for President Obama -- who makes his NCAA predictions in the Oval Office each year -- it's clear that Americans embrace gaming."
The AGA estimates that $7 billion of the $9 billion bet on the tournament will be done so illegally. Accurately gauging how much is illegally wagered, of course, is difficult, because bookies on the corner don't publicly report earnings. Neither do the offshore books that handle the bulk of Americans' bets.
It's also a challenge to pinpoint how much money is wagered on the tournament at Nevada's legal sportsbooks. The consensus estimate among Las Vegas bookmakers is $100 million to $200 million statewide. The AGA estimates $240 million.
"I'd take the low end on that," Las Vegas veteran Jimmy Vaccaro of the South Point sportsbook said.
Nevada Gaming Control does not track the betting action on the tournament and includes college and professional basketball in one "basketball" category in the monthly revenue reports. But the impact of the tournament is obvious.
Over the past five years, an average of $294.6 million has been wagered on basketball in March at Nevada books. Over the same time period, an average of $140.0 million has been bet on basketball in February at the state's books.
Vaccaro, whose Vegas bookmaking career began in the 1970s, says the NCAA tournament didn't attract much attention in his early days. The 1979 championship game between Magic Johnson's favored Michigan State Spartans and Larry Bird's Indiana State Sycamores is the first big college basketball game he remembers generating any buzz, but even that game drew limited betting action.
"There was no rush to the window," Vaccaro said. "I had to remind guys to get their bets in before the game started."
Reminders aren't necessary anymore. These days, lines start forming at the betting windows early in the morning on the opening Thursday and Friday of the tournament. (The Mirage sportsbook will open at 5:30 a.m. PT next week.) The tournament has blossomed into one of the biggest events of the Las Vegas calendar, which is probably not what the NCAA envisioned when it expanded the tournament to 64 teams in 1985.
In March 1988, $79.2 million was wagered on basketball at Nevada books. That February, $78.3 million was bet on basketball. The past two years, the amount wagered on basketball in March eclipsed $300 million, more than double than what was bet the past two Februarys.
"It continues to grow," said John Avello, executive director of the Wynn race and sportsbook. "I'd say it's up 10-15 percent seems like every year."
Avello took a $1 million bet on the New England Patriots in the Super Bowl. He says he won't take any that size during the NCAA tournament. He expects some six-figure wagers on the Final Four and championship game and plenty of five-figure bets in the earlier rounds. Bookmakers say, however, the most common size of wager during the first two days of the tournament is $25.
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