explaining a finding

["Jackson, Shelly L *HS" <SLJ4U@xxxxxxxxxxxxxxxxxxxxxxxx>]

In the study cited below, Finkelhor et al. (1990) found that "Boys were more likely to be abused by strangers (40% vs. 21% for women), whereas girls were more likely to be abused by family members (29% vs. 11%)." (p. 21). What are the plausible explanations for this finding?
 
Finkelhor, D., Hotaling, G., Lewis, I. A., & Smith, C. (1990). Sexual abuse in a national survey of adult men and women: Prevalence, characteristics, and risk factors. Child Abuse & Neglect, 14, 19-28.