Up 3.4% in last three years. Many are returnees who violated rules of probation.

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After a brief decline, Wisconsin’s prison inmate population has begun to grow again, raising the prospect of increasing costs for taxpayers and renewed pressures on state finances, according to a new report from the Wisconsin Taxpayers Alliance (WISTAX). Now in its 85th year, WISTAX is a nonpartisan organization dedicated to public policy research and citizen education.

The number of inmates rose 3.4% between 2013 and 2016, to 22,918, after a 3.2% decline in the three previous years, WISTAX found. The proposed 2017-19 state budget projects an increase of 1.8% this year, followed by a 0.4% decline, to a total of 23,233 by mid-2019.

The report, “Inside Wisconsin Corrections,” identifies several major factors in the population growth. One is that the violent crime rate is rising in Wisconsin, even as it has declined nationally. Another is that inmates are serving longer terms. Additionally, prison admissions are increasing due to a growing number of inmates released under extended supervision and then returned to prison for rule violations or new crimes. Changes in state laws, such as longer sentences or mandatory prison time for some drunken driving offenses, also play a role.

The report also profiles the current inmate population, which is generally older and serving more time behind bars than a decade ago. In 2006, inmates under age 29 comprised nearly 39% of the prison population; in 2016, they were only 30%, while inmates from 30 to 39 rose from 29% to 31%. The share of those over 50 nearly doubled, from 10% to 19%. Meanwhile, the share of inmates serving five years or more rose from 28% in 2006 to 36% in 2016, while those serving one to two years dropped from 41% to 36%.

The proportion of inmates serving time for violent offenses also has increased, from 59% in 2006 to 67% in 2016. As violent offenders tend to draw longer sentences, this increase may explain why inmates’ terms are longer. The share of “public order” offenders, which includes drunken drivers, has also increased, from 8% to almost 9%; in recent years, lawmakers have increased penalties for these offenses.

The WISTAX report also analyzes the impact of the state’s “truth in sentencing” (TIS) law, which took effect in 2000, on prison admissions and inmate population growth. TIS eliminated parole, which allowed the discretionary early release of inmates, and instead requires inmates to serve a specified time behind bars followed by a period of extended community supervision.

Nearly a third (31%) of prison admissions in 2015 were offenders returned to prison for violating rules of extended supervision. Prior to TIS, offenders violating parole received credit for “street time” and could be returned to prison only to serve the time remaining on their sentence. Under TIS, however, there is no credit for “street time,” so offenders returned to prison for violations could serve the entire term of their extended supervision; this, in turn, may result in inmates serving longer terms.

WISTAX also reviews the growth of Wisconsin’s inmate population and its impact on state spending over the past two-and-a-half decades. As in many other states, Wisconsin saw a major increase in inmate numbers in the 1990s, nearly tripling from 7,332 inmates in 1990 to 20,111 in 1999.

The increase produced a prison building boom, with 12 new correctional facilities and nearly 7,000 new beds. Some inmates were sent to prisons in other states or housed in Wisconsin county jails. Between 1997 and 2007, spending rose 110%, to $1.07 billion. As a share of the state’s general fund budget, Department of Corrections spending grew from 3% in 1990 to more than 6% in 1999.

Growth slowed from 2000 to 2007, rising a total of 14%, with the inmate population reaching its peak of 23,184 in 2007. Spending rose 46% in the seven years, with corrections reaching 8% of the general fund budget. After peaking at 9% of the state’s general fund budget in 2009, Corrections dropped to under 8% in 2016.

The report notes Wisconsin’s incarceration rate has increased during the period studied, from 201 inmates per 100,000 residents in 1995 to 377 in 2015. Among the five states in the upper Midwest, Wisconsin’s rate is now second-highest, behind Michigan.