T he Bureau of Prisons (BOP) is the largest correctional agency in the country in terms of the number of prisoners under its jurisdiction. BOP was established in 1930 to house federal inmates, professionalize the prison service, and ensure consistent and centralized administration of the federal prison system. BOP must confine any offender convicted and sentenced to a term of imprisonment in a federal court. Changes in federal criminal justice policy since the early 1980s—enforcing a growing number of federal crimes, replacing indeterminate sentencing with a determinate sentencing structure through sentencing guidelines, and increasing the number of federal offenses subject to mandatory minimum sentences—led to rapid growth in the federal prison population. The total number of inmates under BOP's jurisdiction increased from approximately 25,000 in FY1980 to over 219,000 in FY2013. Between FY1980 and FY2013, the federal prison population increased, on average, by approximately 5,900 inmates annually. However, since the peak in FY2013, the number of inmates in the federal prison system decreased each subsequent fiscal year to approximately 192,000 inmates in FY2016. Generally, the increase in the federal prison population necessitated an increase in appropriations for BOP's operations and infrastructure. In FY1980, Congress appropriated $330.0 million for BOP; by FY2016, the total appropriation for BOP reached $7.479 billion , which was the largest nominal appropriation ever for BOP. Appropriations for BOP have generally continued to increase since FY2013 (FY2017 was the exception) even though the prison population has decreased since that time. Increasing appropriations for BOP, despite the declining prison population, could be the result of a growing per capita cost of incarceration or BOP's need to maintain staffing levels commensurate with the size of the prison population. This report provides an overview of BOP's appropriations since FY1980. Specifically, this report examines trends in BOP's total appropriations, changes in funding for BOP's appropriations account, and trends in funding for the decision units under BOP's appropriations accounts. The report provides a brief analysis of how the Administration's requested funding for BOP compares to enacted appropriations. It also discusses changes in the per capita cost of incarceration and how appropriations for BOP have changed relative to those for the Department of Justice, both issues that have been of interest to policymakers. As shown in Figure 1 , BOP's appropriations increased by nearly $7.149 billion from FY1980 to FY2016. FY2016 was the peak, in nominal terms, for BOP's funding. BOP's funding decreased by $340 million in FY2017. Between FY1980 and FY2016, the average annual increase in BOP's appropriations was approximately $199 million. The increasing appropriations for BOP generally coincided with an increase in the number of inmates under BOP's jurisdiction. This trend changed somewhat in recent years. BOP's appropriations increased each fiscal year from FY2014 to FY2016 even though the total number of federal inmates decreased in each of those fiscal years. Figure 1 also shows that BOP's appropriations have increased at a rate that is significantly greater than inflation, as indicated by the positive slope on the inflation-adjusted line in the figure. In FY2017 inflation-adjusted dollars, BOP's appropriations increased 787% from FY1980 to FY2016. BOP's appropriations increased 732%, in inflation-adjusted dollars, when accounting for the decrease in appropriations for FY2017. It has been argued that even though appropriations for BOP are discretionary, they are effectively mandatory because "[b]y law, the BOP must accept and provide for all [f]ederal inmates, including but not limited to inmate care, custodial staff, contract beds, food, and medical costs. BOP cannot control the number of inmates sentenced to prison, and unlike other [f]ederal agencies, cannot limit assigned workloads and thereby control operating costs." Nearly all of BOP's operations are funded through annual appropriations provided by Congress. BOP's annual budget is divided between two major accounts: Salaries and Expenses (S&E) and Buildings and Facilities (B&F). The S&E account (i.e., the operating budget) provides for the custody and care of federal inmates and for the daily maintenance and operations of correctional facilities, regional offices, and BOP's central office in Washington, DC. It also provides funding for the incarceration of federal inmates in state, local, and private facilities. The B&F account (i.e., the capital budget) provides funding for the construction of new facilities and the modernization, repair, and expansion of existing facilities. Two trends emerge from a review of BOP's appropriations from FY1980 through FY2017. First, while there has been a nearly continuous increase in the overall appropriations for BOP, it is in large part driven by an almost continuous increase in appropriations for BOP's Salaries and Expenses (S&E) account since FY1980 (see Figure 2 ). The one exception to this trend is the appropriation for FY2013, which is lower than the FY2012 appropriation due to the sequestration ordered pursuant to the Budget Control Act of 2011 ( P.L. 112-25 ). In general, appropriations for BOP's S&E account increased as the prison population increased, which is not surprising given that the S&E account funds the operation of the federal prison system, including the salaries and benefits of both correctional officers and other institutional employees. BOP hired more officers and other employees as it opened more prisons and supervised more inmates. However, funding for the S&E account has continued to increase, albeit at a reduced rate, even though the prison population has decreased each fiscal year from FY2013 to FY2016. BOP has continued to request increased funding for the S&E account even though it is housing fewer inmates, and Congress has continued to increase appropriations, though generally below the level requested. BOP notes that additional funding is needed to cover the cost of pay raises and benefits for employees, as well as to cover growing costs associated with inmate health care, food, and prison utilities. Also, during some of these years, BOP requested additional funding to increase its capacity to provide programs and services for inmates (e.g., reentry programming and mental health treatment) and to hire more staff to increase institutional safety, something BOP might not have been able to do during the years when the inmate population was growing at a sustained clip and resources were dedicated to providing basic levels of care and security. In addition, even though there are fewer inmates under the BOP's jurisdiction, the federal prison system is still operating over its rated capacity. In short, the federal prison population has not declined enough that BOP could start to close prisons and reduce staff, which would help bring down the cost of the federal prison system. Second, funding for the Buildings and Facilities (B&F) account is more irregular, with Congress appropriating more in some fiscal years and less in others. The irregularity in B&F funding is likely the result of the cyclical nature of the expansion of BOP's prison capacity as more offenders entered the federal prison system. Congress would appropriate funding to help boost bedspace in the federal prison system; BOP would use that funding to plan and construct new prisons. Upon completion of the new prison, BOP's capacity would expand, but it would need to expand again in later years as the prison population continued to grow, and the cycle would begin anew. In FY2017, a $400 million decrease in funding for the B&F account was the primary reason why BOP's total appropriation decreased for FY2017. Each of BOP's two appropriations accounts are divided into decision units, each of which fund specific aspects of BOP operations. The S&E account is divided into four decision units: Inmate Care and Programs : This decision unit covers the cost of inmate food, medical supplies, institutional and release clothing, welfare services, transportation, gratuities, staff salaries, and other operational costs directly related to providing inmate care. It provides funding for inmate programs, including education and vocational training, psychological services, religious programs, and drug treatment. This decision unit also covers costs associated with regional and central office administration and support related to providing inmate care. Institution Security and Administration : This decision unit funds institution maintenance, motor pool operations, powerhouse operations, institution security, and other administrative functions. It also covers costs associated with regional and central office administrative and management support functions such as research and evaluation, systems support, financial management, budget functions, safety, and legal counsel. Contract Confinement : This decision unit provides for the costs associated with the confinement of federal inmates in contract facilities, which include private prisons, Residential Reentry Centers (RRC), state and local facilities, and home confinement. It provides funding for the management and oversight of contract confinement functions. This decision unit also provides funding for the National Institute of Corrections (NIC). Management and Administration : This decision unit provides funding for costs associated with general administration and provides funding for BOP's central office, regional offices, and staff training centers. Since FY1999, approximately 80% of BOP's S&E funding has gone to combined appropriations for the Inmate Care and Programs and the Institution Security and Administration decision units. Funding for these two decision units has increased at about the same rate as funding for the S&E account overall. From FY1999 to FY2017, funding for the Inmate Care and Programs decision unit increased 141% and funding for the Institution Security and Administration decision unit increased 123%. In comparison, funding for the S&E account increased 143% over the same time period. Funding for the Contract Confinement decision unit increased 295% between FY1999 and FY2017.