A new study from the University of Minnesota finds 8 percent of people who attend professional sporting events leave too drunk to drive.
Researchers set up breathalyzer machines outside two stadiums -- football and baseball -- and asked for volunteers to have their blood alcohol level tested when they left the venues.
Eight percent of the people tested had a blood alcohol level above the legal driving limit of .08 percent, according to University of Minnesota Public Health professor Darin Erickson.
He said the results may seem obvious. But until now, policy makers and others studying alcohol use had little data to work with.
"There really wasn't much in terms of scientific study of it," he said. "It's one thing to know going in that people are consuming, but what we really want to do is validate that in an objective, systematic way."
Erickson also said people who tailgate before a game are more likely to leave drunk afterward.
Because of ethics guidelines, he could not say where the data were gathered.
The study is published in the journal Alcoholism: Clinical & Experimental Research.