Explanation is for 2014:
At yearend 2014, the United States held an estimated 1,561,500 prisoners in state and federal correctional facilities, a decrease of approximately 15,400 prisoners (down 1%) from December 31, 2013. A third (34%) of the decrease was due to fewer prisoners under the jurisdiction of the Federal Bureau of Prisons (BOP), which declined for the second consecutive year (figure 1).
Prisoners sentenced to more than 1 year in state or federal prison declined by almost 1% (down 11,800 prison inmates) from yearend 2013 (1,520,400) to yearend 2014 (1,508,600).
The number of prisoners housed in private facilities in the United States decrease.
The statistics in this report are based on the Bureau of Justice Statistics’ (BJS) National Prisoner Statistics (NPS) program, which collects annual data from state DOCs and the BOP on prisoner counts, prisoner characteristics, admissions, releases, and prison capacity. The 2014 NPS collection is number 90 in a series that began in 1926. Forty-nine states and the BOP reported NPS data for 2014, while data for Alaska were obtained from other sources or imputed. (See Methodology.)
If you search the PDF files for "sex" you will find stats specific to sex offenses/rape. These can be valuable for reporting. ex: one year vs the next, etc.. Also figures are broken down between federal and state prisoners; very valuable>
Prisoners in 2015
Prisoners in 2014
Prisoners in 2013