Illegal wagers: $60-$70 billion
"The NFL used to be a dominant No. 1 in the betting world. Not anymore," Root says. "College football is a close No. 2 and gaining fast. Betting is driven by college graduates who learned to bet on sports while attending colleges with great football rivalries like Michigan, Ohio State, Florida, Georgia, Tennessee, Texas, Notre Dame, USC, etc. If you attended those colleges, and you enjoy gambling, it's natural for you to bet college football for the rest of your life."