Adolescent gambling in Minnesota before and after the institution of a Statewide lottery was examined by prominent gambling researchers Ken C. Winters and Randy D. Stinchfield, both of the University of Minnesota. Their research concluded that gambling is common yet relatively problem-free for most Minnesota youth. Yet, at the follow-up interview many youth (3.5% to 9.5% depending on the criteria used) were gambling at problem levels. All significant increases in gambling frequency occurred exclusively for games which were legal for adults.