It's coming from two different sources, including the uniform crime reporting survey, which covers 99% of all police forces in the country. The uniform crime reporting survey collects detailed information about each criminal incident being reported to the police, and it collects information about the offenders when there is an identified offender or accused. It also collects some basic demographics information about the victims, when this is a violent offence such as human trafficking, for example.
On February 27th, 2018. See this statement in context.