Only 22 percent of bicyclists in severe accidents were wearing helmets - The Washington Post

Although head injuries from biking accidents can be severe, most adults don’t wear helmets. Only 22 percent of adults seriously injured while biking were using a helmet at the time of their accident, according to information from the National Trauma Data Bank on 76,032 bicyclists who sustained head or neck injuries from 2002 to 2012.....
https://www.washingtonpost.com/health/the-big-number-only-22-percent-of-bicyclists-in-severe-accidents-were-wearing-helmets/2019/09/13/81046e72-d56a-11e9-86ac-0f250cc91758_story.html