While incarceration rates have begun to decline nationally, some states expect to put more prisoners behind bars in coming years.

The Pew Charitable Trusts’ public safety performance project published new state prison population projections Tuesday, providing projections of how numbers of inmates could change over the next four years.

A dozen of the 34 states reporting data expect their prison populations to grow more than 5 percent. The number of inmates housed in Iowa state correctional facilities is slated to climb 16 percent by 2018 -- the largest increase of any state. Wyoming (14 percent) and Alaska (11 percent) also reported larger projected growth.

Overall, the total prison population in states reporting data is expected to swell 3 percent over the next four years. If projections hold true, that means the state imprisonment rate should remain about unchanged when adjusted for population growth.

At least six states expect their prison populations to shrink -- albeit not by much -- in the coming years.

“The fastest [prison population] growing states tend to be those that have not put together bipartisan task forces over the last couple years to tackle their growth,” said Adam Gelb, director of Pew’s Public Safety Performance Project.

State Incarceration Projections

The following table shows projections compiled by Pew for the 34 states reporting data:

         
State 2014 Prison Population Projected 2018 Projected Change Projected % Change
Alaska 5,111 5,686 575 11%
Arizona 41,773 45,613 3,840 9%
Arkansas 17,327 18,620 1,293 7%
California 135,430 144,633 9,203 7%
Colorado 20,522 21,837 1,315 6%
Florida 100,942 102,660 1,718 2%
Hawaii 5,298 5,277 -21 0%
Idaho 8,267 8,270 3 0%
Iowa 8,119 9,408 1,289 16%
Kansas 9,612 9,735 123 1%
Kentucky 20,989 21,720 731 3%
Louisiana 39,100 38,077 -1,023 -3%
Maine 2,116 2,127 11 1%
Massachusetts 10,898 10,672 -226 -2%
Minnesota 9,929 10,328 399 4%
Montana 2,581 2,682 101 4%
Nebraska 5,064 5,424 360 7%
Nevada 12,984 13,276 292 2%
New Mexico 7,021 7,377 356 5%
North Carolina 37,679 37,419 -260 -1%
Ohio 50,214 50,696 482 1%
Oregon 14,721 14,577 -144 -1%
Pennsylvania 51,118 47,848 -3,270 -6%
Rhode Island 3,213 3,338 125 4%
South Dakota 3,636 3,704 68 2%
Tennessee 25,524 27,909 2,385 9%
Texas 151,045 152,292 1,247 1%
Utah 7,214 7,782 568 8%
Vermont 2,119 2,247 128 6%
Virginia 37,843 39,440 1,597 4%
Washington 17,601 18,248 647 4%
West Virginia 7,637 7,943 306 4%
Wyoming 2,068 2,348 280 14%

SOURCES: State agencies, The Pew Charitable Trusts, Council of State Governments Justice Center, JFA Institute An earlier Pew analysis found 32 states recording declines in both imprisonment and crime rates since 2008. The trends show, according to Gelb, that prison populations don’t need to expand for crime rates to drop.

States pursed a variety of approaches in recent years that helped to push down or limit prison populations. Some reclassified minor drug and property offenses. Revisions to mandatory minimum sentencing laws also provided judges with greater leeway in sentencing. Georgia, for example, approved a law in 2013 allowing judges to impose shorter sentences for certain sexual and violent offenses when prosecutors and defense attorneys both agree the circumstances don’t fit such longer sentences.

Tight budgets and overcrowded prisons often gave lawmakers incentive to pursue reforms. States weren’t all under the same pressure, though, and many measures weren’t budget-driven, Gelb said.

Regardless of how total prison populations fluctuate in the coming years, the number of aging prisoners will rise as baby boomers grow older. A few states have explored early release programs and other efforts aimed at this demographic group.

Prison facilities in some states with projected growth have already exceeded capacity.

The Bureau of Justice Statistics published updated data earlier this fall comparing numbers of inmates in custody to states’ prison capacities. About half of states reporting data were at 99 percent or more of their operational capacity at the end of last year.

State Prison Capacities

Figures listed below show state inmate populations as a percentage of prison capacity, current as of Dec. 31, 2013.

Data Definitions

       
Jurisdiction % Operational Capacity % Rated Capacity % Design Capacity
Alabama 100 -- 197
Alaska -- -- --
Arizona 82 94 94
Arkansas 99 99 103
California -- -- 143
Colorado 115 -- 124
Connecticut -- -- --
Delaware 130 118 163
Florida 88 -- --
Georgia 98 89 --
Hawaii 113 -- 164
Idaho 104 -- 103
Illinois 152 152 173
Indiana 92 -- --
Iowa -- -- 114
Kansas 103 104 104
Kentucky 93 100 88
Louisiana 121 104 112
Maine 102 89 89
Maryland 92 -- --
Massachusetts -- -- 132
Michigan 99 97 --
Minnesota 103 -- --
Mississippi 61 -- --
Missouri 99 -- --
Montana -- 99 --
Nebraska 126 -- 158
Nevada -- -- --
New Hampshire 100 -- 130
New Jersey 93 100 85
New Mexico 51 58 51
New York 100 101 102
North Carolina 95 -- 111
North Dakota 159 150 150
Ohio -- 132 --
Oklahoma 98 98 98
Oregon -- -- 102
Pennsylvania 104 104 104
Rhode Island 84 79 80
South Carolina 90 -- --
South Dakota 99 -- --
Tennessee 73 70 --
Texas 91 87 87
Utah 75 -- 72
Vermont 94 94 119
Virginia -- 90 --
Washington 108 106 --
West Virginia 99 115 115
Wisconsin 98 -- 131
Wyoming 89 89 85

NOTE: Figures not shown were either unavailable or not reported by states. See appendix table 1 in "Prisoners in 2013" published by BJS for notes on individual states. SOURCE: Bureau of Justice Statistics Operational Capacity: Number of inmates that "can be accommodated based on a facility's staff, existing programs and services." Rated Capacity: Assigned by rating officials Design Capacity: Refers to how many inmates architects/planners originally intended for facilities