Encyclopedia of Psychology and Law

who are confined in American jails and prisons and in

part because of several well-known court cases in

which states have been ordered to improve the condi-

tions of confinement to include alleviating overcrowd-

ing. However, prison overcrowding is neither a

particularly new nor an exclusively American prob-

lem. With the advent of the prisoners’ rights move-

ment in the early 1970s, prison conditions have come

under increased scrutiny. One such area of increased

scrutiny is the degree to which the inmate population

exceeds the rated capacity of the institution in which

it is housed. Furthermore, concerns about prison over-

crowding extend beyond the borders of the United

States. Canada, Great Britain, and the Scandinavian

countries have recently raised concerns about prison

overcrowding, and many nations in Africa, Asia, and

South America have prisons that are more crowded

than those in the United States.

Measurement

Prison overcrowding has traditionally been defined

by density (i.e., the proportion of inmates to rated

capacity of an institution; the ratio of single cells to

multiple-person cells). A distinction can be drawn,

however, between overcrowding and density. Whereas

overcrowding is a psychological condition based on a

perception of limited space by an incarcerated indi-

vidual, density is a physical condition, such as the

ratio of inmates to available space in an institution.

There are two forms of density: spatial density and

social density. Spatial density, the measure most often

used in prison-overcrowding research, is normally

calculated as the proportion of inmates in an institu-

tion or prison system to the available space as estab-

lished by the rated capacity of the institution or

system. Prison and jail officials often consider their

institutions overcrowded when they exceed 80% of

the rated capacity. Social density, on the other hand, is

measured by the amount of double and triple bunking

found in a correctional institution. Research indicates

that inmate health problems and violence may rise as

social density increases.

Causes

The overriding cause of prison overcrowding is fairly

obvious: The number of inmates exceeds the spatial

and social capacity of correctional institutions and

prison systems to house these inmates. On the other

hand, the underlying cause of this surplus of inmates

is less apparent. Several sets of factors appear to have

contributed to the growth of jail and prison popula-

tions in the United States and other parts of the world.

One important factor, at least in the United States, is a

punitive public. Many people in the United States

want to see those who violate society’s rules punished

for their actions. Politicians frequently comply with the

public’s demand for greater punishment because they

do not want to appear weak on crime. Accordingly,

they introduce legislation that provides for mandatory,

determinate, or longer sentences; reduces good-

conduct time credit; and restricts or eliminates early-

release programs such as parole.

In addition to the legislative response of politicians

and policymakers to a punitive public, there are several

other factors that may contribute to prison overcrowd-

ing. Drug use is instrumental in a quarter to a third of

all new jail and prison admissions and is the leading

cause of parole and conditional release violation. As

such, drugs are both directly and indirectly (harsher

sentences for drug offenses) linked to prison over-

crowding. Demographic changes contribute to prison

overcrowding, as exemplified by the crime explosion

of the mid-1960s when the baby boomers were in the

age range most conducive to crime (late teens to mid-

20s). Over time, prisons age and become less efficient;

some may even be closed. This places an increased

burden on existing facilities and adds to the growing

overcrowding problem. With advances in technology,

law enforcement may become more efficient, which

could potentially increase the jail and prison popula-

tions and contribute to prison overcrowding.

Consequences

The most frequently mentioned consequence of prison

overcrowding is aggression. Early research on over-

crowding in rodents indicated that mice and rats

raised in a crowded environment were more violent,

stressed, and diseased than mice and rats raised in an

uncrowded environment. Studies conducted on prison

overcrowding, however, have yielded mixed results.

In some studies, prison overcrowding has been found

to correspond to an increase in future disciplinary

problems, particularly aggression. In other studies,

prison overcrowding has failed to correlate with

aggressive and nonaggressive disciplinary problems.

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