One third of street-level prostitutes in the U.S. are less 18 years old while fifty percent of off-street prostitutes are less than 18 years old. Off-street prostitution includes massage parlors, strip clubs, and escort services. According to Estes and Weiner, 12 to 14 is the average age of entry into prostitution for girls under 17 years old in the United States while the average age of entry into prostitution is between 11 and 13.