In 2001, the University of Pennsylvania School of Social Work released a study on CSEC conducted in 17 cities across the United States. While they did not interview any of the adolescent subjects of the inquiry, they estimated through secondary response that as many as 300,000 American youth may be at risk of commercial sexual exploitation at any time. However, the actual number of children involved in prostitution is likely to be much smaller: over 10 years only 827 cases a year had been reported to police departments. The Center for Court Innovation in New York City had used Respondent Driven Sampling (RDS), Social Network Analysis, capture/recapture, and Markov based probability estimates in 2008 to generate a prevalence estimate for New York City that suggested far fewer commercially sexually exploited children than the 300,000 and far more than the 827 suggested by these two most widely read sources.