From 1980 motorcycle ownership among riders aged 40 and over increased dramatically, from 15.1 percent of all riders in 1980 to 43.7 percent in 1998. The mean engine displacement of the motorcycles involved in fatal crashes also increased, from an average engine size of in 1990, to in 2001, an increase of 24.7 percent. It has been suggested that the combination of older riders on higher-powered motorcycles might have been partially responsible for the increase in motorcycle deaths from the late 1990s until 2004. Blunt abdominal trauma can be caused by a motorcycle accident, and can damage the testes and intestines.