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Incarceration Trends aims to inform the public dialogue, advance research, and help guide change by providing easily accessible information on the number of individuals in jail and prison for every county in the U.S.
County jail population: These data were obtained from the Bureau of Justice Statistics (BJS) Annual Survey of Jails (ASJ) and Census of Jails (COJ). The ASJ has been fielded 25 times between 1985 and 2014 and captures data for a sample of a few hundred jails; in 2014, the sample was approximately 800 counties, which included the 250 largest jails. The COJ has been fielded 10 times since 1970—in 1970, 1972, 1978, 1983, 1988, 1993, 1999, 2005, 2006, and 2013—but captures data for all counties. Data for years that counties do not supply data (through the ASJ or COJ) are interpolated assuming a constant rate of change between the years when data are provided. Six states (Alaska, Connecticut, Delaware, Hawaii, Rhode Island, and Vermont) do not participate in the U.S. jail survey or census because they run unified state systems that combine prisons and jails.
Total jail population is the average daily population and excludes federal jails and inmates in local jails held for federal authorities, such as U.S. Immigration and Customs Enforcement and U.S. Marshals Service. Federal inmates are, however, included in pretrial, race, gender, and admissions data because the BJS surveys do not disaggregate inmate jurisdiction for these data. The Pretrial jail population is those individuals categorized as “unconvicted” in the BJS data. See Kang, Brown 2015 for more information.
The pretrial jail population is a June 30th snapshot and are those individuals categorized as “unconvicted” in the BJS data. The total jail population and pretrial population numbers are not directly comparable because the total jail population is based on the average daily jail population in that year rather than a single day (June 30) count. Single-day counts tend to fluctuate more than the average daily population.
