The corresponding average annual prison population growth rate during this period was 8.5 percent (9.9 percent for the federal population and 8.4 percent for the state populations). The state prison population grew from 305,458 inmates in 1980 to 1,026,882 inmates in 1995, which is an increase of about 236 percent. Particularly noteworthy has been the trend regarding drug offenders as a percentage of the total inmate population. In June 1996, BOP projected that the federal prison population could reach about 125,000 inmates by 2000, which is a 25-percent increase over the 1995 level (see table 1). In July 1995, NCCD projected that, under sentencing policies in effect in 1994, the total inmate population for federal and state prisons could reach 1.4 million by 2000, which is an increase of 24 percent over the 1995 level. As figure 3 shows, total U.S. prison operating costs grew from about $3.1 billion in fiscal year 1980 to about $17.7 billion in current dollars in fiscal year 1994. BOP also projected that its capital costs for new federal prisons scheduled to begin operations during fiscal years 1996 to 2006 could total about $4 billion. Models and Methodologies Used to Project Prison Populations

BOP, NCCD, California, and Texas each use microsimulation models to project prison inmate populations. For example, according to BOP, its projections of federal prison inmate populations for 1991 to 1995 were within 1.4 percent (on average) of the actual populations. Objectives, Scope, and Methodology

We initiated this review to identify (1) the trends in federal and state prison inmate populations and operating and capital costs since 1980, including projections for 2000 and beyond and the reasons for these trendsand (2) the models and methodologies used by federal and statecorrections agencies and nongovernmental forecasting organizations to make these projections, including whether any validity or reliability assessments had been done. In 1987, BOP and the U.S.
Why GAO Did This Study

GAO reviewed the trends in U.S. prison inmate populations and operating and capital costs since 1980, including projections for 2000 and beyond and the reasons for the trends and the models and methodologies used by federal and state corrections agencies and nongovernmental forecasting organizations to make these projections.

What GAO Found

GAO found that: (1) the total U.S. prison population grew from about 329,800 inmates in 1980 to about 1.1 million inmates in 1995, which is an increase of about 242 percent; (2) during this period, the federal inmate population grew about 311 percent, and the inmate populations under the jurisdiction of state prisons grew about 237 percent; (3) the corresponding average annual growth rates were 9.9 percent of federal populations and 8.4 percent for state populations; (4) in June 1996, the Bureau of Prisons (BOP) projected that the federal prison population could reach about 125,000 inmates by 2000, an increase of 25 percent over the 1995 level; (5) in July 1995, the National Council on Crime and Delinquency (NCCD) projected that the total federal and state prison population under sentencing policies in effect in 1994 could reach 1.4 million inmates by 2000, representing an increase of about 24 percent over the 1995 level; (6) in recent years, inmate population growth can be traced in large part to major legislative initiatives that are intended to get tough on crime, particularly on drug offenders; (7) U.S. prison annual operating costs grew from about $3.1 billion in fiscal year (FY) 1980 to about $17.7 billion in current dollars in FY 1994; (8) BOP projected that its capital costs for new federal prisons scheduled to begin operations during fiscal years 1996 to 2006 could total about $4 billion; (9) BOP, NCCD, California, and Texas each use a form of microsimulation modeling to forecast prison inmate populations; and (10) according to BOP, its projections of federal prison inmate populations for 1991 to 1995 were within 1.4 percent, on average, of the actual populations.