These data are part of NACJD's Fast Track Release and are distributed as they were received from the data depositor. The files have been zipped by NACJD for release, but not checked or processed except for the removal of direct identifiers. Users should refer to the accompanying readme file for a brief description of the files available with this collection and consult the investigator(s) if further information is needed. This study measures the size and structure of the underground commercial sex economy in eight major US cities: San Diego, Seattle, Dallas, Denver, Washington, DC, Kansas City, Atlanta, and Miami. The goals of this study were to derive a more rigorous estimate of the underground commercial sex economy (UCSE) in eight major US cities and to provide an understanding of the structure of this underground economy. Researchers relied on a multi-method approach using both qualitative and quantitative data to estimate the size of UCSE including: Collecting official data on crime related to the underground weapons and drugs economies Conducting semi-structured interviews with convicted traffickers, pimps, child pornographers, and sex workers at the federal, state, and local levels Conducting semi-structured interviews with local and federal police investigators and prosecutors to inform our analysis of the interrelationship across different types of underground commercial sex activity.