These age-related differences in morbidity risk likely come from several sources. First, society allows older children, but not younger ones, to participate in riskier activities, such as driving a car. Second, the increased size, weight, and strength of older children increases the risks they pose to their contemporaries in daily life, especially when playing sports. Third, reasonable parents often allow adolescents, but not younger children, to engage in activities such as ice skating and hiking that pose risks without adult supervision. Fourth, adolescents are more likely than younger children to engage in inappropriate activities and behave recklessly.