Betting on March Madness is starting with many gamblers throwing their weight behind Duke and freshman phenom Zion Williamson.

William Hill US says nearly 20 percent of the money bet on the NCAA Tournament winner over the past year has backed the Blue Devils, who were listed as a 2-1 favorite in odds adjusted following the release of the bracket.

The sportsbook operator says 9 percent of the actual wagers have come in on Gonzaga or Duke, meaning the Bulldogs are popular but gamblers placing more expensive bets are backing the Blue Devils, top seed in the East.

Virginia and Gonzaga are each listed at 6-1 odds to win the title, while North Carolina is 8-1.

Betting on March Madness is shifting this year with the expansion of legalized sports gambling beyond Nevada. New Jersey, Rhode Island and several other states have legalized sports betting since a U.S. Supreme Court ruling last year