ISO | Jail Statistics and what the numbers show.

Highlights

County and city jails held 745,200 inmates at midyear 2017, down from 780,200 at midyear 2007.
The jail incarceration rate declined from 259 inmates per 100,000 U.S. residents in midyear 2007 to 229 per 100,000 at midyear 2017, a 12% decrease.
In 2017, males were incarcerated in jail at a rate (394 per 100,000 male U.S. residents) 5.7 times that of females (69 per 100,000 female U.S. residents).
In 2017, jails reported 10.6 million admissions, a 19% decline from 2007.
The estimated average time in jail in 2017 was 26 days.

The total rated capacity of county and city jails was 915,100 beds at midyear 2017.
An estimated 81% of jail beds were occupied in 2017, down from 95% in 2005.
From 2005 to 2017, the jail incarceration rate for whites increased by 12%, while the rate for blacks decreased by 23%.
The male incarceration rate dropped from 448 per 100,000 male residents in 2005 to 394 per 100,000 in 2017, a 12% drop.
Jails employed 225,700 full-time staff at midyear 2017, and the inmate-to-correctional-officer ratio was 4.2 to 1.

*Data can be found from in a report done by Zhen Zeng, Ph.D., BJS Statistician titled "Jail Inmates in 2017"

Over 1.5 million inmates are held in state or federal prison and local jails.
Approximately 1 in every 35 US adult residents is under some form of correctional control (in prison or jail or on probation or parole).
93% of state and federal prisoners are male.
The incarceration rate for white males is 465 per 100,000 residents.
The incarceration rate for Hispanic males is 1,090 per 100,000 residents.
The incarceration rate for black males is 2,724 per 100,000 residents. Black males ages 18 to 19 are ten times more likely to be in state or federal prison than whites.
Black males ages 30 to 34 have the highest custody incarceration rate of any race, age, or gender group.

*More statistics can be found at Bureau of Justice Statistics

Education programs decrease recidivism.
Substance abuse programs decrease recidivism.
Offenders who complete substance abuse programs in jail are successful after release.
Inmates who earn a GED are less likely to recidivate than those who do not complete a program.
Inmates with a Vocational Certificate at release were are less likely to recidivate than inmates overall.