Total county jail beds, as reported in the Bureau of Justice Statistics’ 2013 Census of Jails. If a county has more than one jail, these capacities are summed.

The total number of individuals incarcerated in a jail facility on a given date.

1. Average daily jail population per 100,000 county residents

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   ((Total jail population during selected date range ÷ number of days in selected date range) ÷ Number of residents in county with selected demographic characteristics) × 100,000

   For example, if a user is viewing the female population for the month of January in County X, the total female jail population for that period is 500, the total population of County X is 10,000, and the female population of County X is 3,000, this will be calculated as: ((500 ÷ 31 days) ÷ 3,000) × 100,000 = 537.6. In other words, there were 537.6 females per 100,000 females residents on average per day in jail in County X during the month of January.

2. Average daily jail population per county detention capacity

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   (Total jail population during selected date range ÷ number of days in selected date range) ÷ Detention capacity of county

   For example, if a user is viewing the female population for the month of January in County X, the total female jail population for that period is 500, and the detention capacity of County X is 1,000, this will be calculated as: (500 ÷ 31 days) ÷ 1,000 = 1.6%. In other words, females made up 1.6% of the county detention capacity on average in County X during the month of January.

A local correctional facility which generally houses individuals who have not been convicted (i.e. people incarcerated pretrial), those with sentences of 1 year or less, those waiting to be transferred to other facilities including prisons or mental health facilities, and/or those with community supervision or bail violations. Jails may also enter into contracts to detain individuals on behalf of other entities, e.g., federal and state governments, and agencies such as U.S. Immigration and Customs Enforcement (ICE).

A publicly available, online log of all individuals detained in a jail facility on a given date. Jail rosters may be updated in real-time, hourly, daily, etc. JDI only collects data from jail rosters that are updated at least daily. A single jail roster may contain information for multiple counties or facilities. For example, West Virginia provides a single online search portal for all jails in the state. Counties may also make more than one jail roster available online.

The number of days an individual is detained in a jail facility for a single booking. Since jail roster scraping may begin after an individual has already been incarcerated, JDI extracts a booking start date from any fields reported on a given roster. For example, if an individual appears in scraped data starting on January 10th, 2022, but their record indicates an admission date of January 1st, 2022, their length of stay is calculated from January 1st, 2022.

The most severe charge reported for an individual, according to the Criminal Justice Administrative Records System (CJARS) Text-based Offense Classification (TOC) algorithm. These are (in order of severity, from most severe to least severe):

1. Violent
2. Property
3. Drug
4. Public Order
5. DUI Offense
6. Criminal traffic

The number of bookings that end during a given week. A booking is considered ended when an individual no longer appears on the roster. It is possible that individuals are transferred to another facility rather than released into the community.

The number of new bookings seen on a jail roster during a given week. A booking is considered new when an individual appears for the first time on the roster.