In the United States overall, the use of private (or for-profit) prisons is a growing trend, but the numbers fluctuate. Between 2000 and 2017, the percentage of private prisons increased by almost 40 percent. One estimate for 2017 places the percentage of inmates held in private prisons at more than eight percent of the state and federal penal system. The number of private prisons and the percentage of inmates they hold vary widely by state; New Mexico has about 50 percent of inmates in private prisons, and Hawaii and Montana each have more than 30 percent. These are among the highest rates. Similarly, the number of inmate deaths per entire inmate population also varies, as does the ratio in public versus private facilities. Official reports on what were formally called Mortality in Correctional Institutions (MCI) are compiled by the Bureau of Justice Statistics of the Department of Justice.
Among the most relevant factors are the number of stays, the length of incarceration, and the facility’s security. Natural causes and suicide account for a large percentage of deaths, and homicide is also significant. Natural causes include age: the longer the stay, the more likely are deaths from natural causes. Overcrowding is also a factor, as it increases the likelihood of transmission of contagious diseases.
One reason for lower levels of natural deaths within private prisons is likely the absence of hospitals as critically ill inmates are transported out of the facility and die elsewhere. In contrast, homicide rates may be higher in private prisons because public facilities have higher security levels. Although people convicted of violent crimes are concentrated in higher security prisons, the security levels, especially in maximum security, may make them safer in terms of effectively deterring homicides.