The volume reviews the recent history of incarceration, tracing successive periods of growth and decline which marked the last 50 years of State prison populations that culminated in the era of rapid growth in the 1970's. Regional components of this trend are presented, showing the dominant role played by southern prison systems in accelerating the overall growth of prison populations. Shifts in the demographic composition of the inmate population are traced, and this population's relationship to the civilian population is briefly examined. In reviewing prison population projection methods, the volume discusses leading indicators of future trends (crime rates, present prison population characteristics, prison facility capacity, unemployment rates) as well as changes in criminal justice policy that can interfere with the outcome validity of trend estimates. The volume presents three series of numerical projections for years up to 1983, each corresponding to a different set of assumptions: (1) an equilibrium exists between costs of imprisonment and the gains expected from further increases in incarceration, and prison capacity will remain unchanged over the next 5 years; (2) the future discrepancy between rates of prisoner intake and release will remain constant; and (3) intake will continue at current rates and releases will lag behind intake by a specified amount. The population projections given can help policymakers gain a fuller appreciation of the forces which determine correctional populations, as well as an understanding of the points at which those forces are exerted. They can also give the policymaker a better sense of the likely ranges within which the populations can be expected to move. State and local use of these projections are discussed. Chapter notes, graphs, charts, and tabular data are supplied, and appendixes present supporting data, State-by-State projection results, projection computation methods, summaries of selected State and local projections reports, and a discussion and data on the relationship between prison populations and prison capacities.