An Institutionalization Effect: The Impact of Mental Hospitalization and Imprisonment on Homicide in the United States, 1934 - 2001 (ICPSR 34986)

Published: May 14, 2014

Principal Investigator(s):
Bernard Harcourt, University of Chicago

Version V1

This data set explored the effect of imprisonment on violent crime rates prior to 1991. Previous research focused exclusively on rates of imprisonment, rather than using a measure that combines institutionalization in both prisons and mental hospitals. Using state-level panel-data regressions over the 68-year period from 1934 to 2001 and controlling for economic conditions, youth population rates, criminal justice enforcement, and demographic factors, this study found a large, robust, and statistically significant relationship between aggregated institutionalization (in mental hospitals and prisons) and homicide rates. This finding provided strong evidence of what should now be called an institutionalization effect -- rather than an imprisonment or incapacitation effect. Demographic information collected include national unemployment rates and institutional race and age composition.

Harcourt, Bernard. An Institutionalization Effect: The Impact of Mental Hospitalization and Imprisonment on Homicide in the United States, 1934 - 2001. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor], 2014-05-14.

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1934 -- 2001


Prision and mental hospital populations

Aggregated interpolated national data was compiled from the following sources: (1) Census Bureau data for decennial years 1940, 1950, and 1960, as well as Census Bureau counts of prisoners and jail inmates for 1923 and 1933; (2) Law Enforcement Assistance Administration (LEAA) census data for 1970; and the BJS jail inmate counts for 1978, 1983, 1988, 1993, 1999, and 2005. Missing years were linearly interpolated using these data.

The data on prison populations were compiled from the Census Bureau reports titled "Prisoners in State and Federal Prisons and Reformatories [year]: Statistics of Prisoners Received and Discharged During the Year, for State and Federal Penal Institutions [year]."

The data on patients in mental hospitals consist of state-by-state panel data with observations running from 1934 to 2001. For the year 1969 and the years 1971 through and including 1995, the American Hospital Association (AHA) collected and published annual data on the average daily census counts for all psychiatric institutions. The data for 1969 and 1971 are average daily census counts at all non-federal psychiatric hospitals; the data for 1972 through 1995 are average daily census counts for all psychiatric institutions, including psychiatric hospitals and institutions for "mental retardation".

administrative records data

aggregate data

census/enumeration data

record abstracts



2014-05-14 ICPSR data undergo a confidentiality review and are altered when necessary to limit the risk of disclosure. ICPSR also routinely creates ready-to-go data files along with setups in the major statistical software formats as well as standard codebooks to accompany the data. In addition to these procedures, ICPSR performed the following processing steps for this data collection:

  • Checked for undocumented or out-of-range codes.


  • Data in this collection are available only to users at ICPSR member institutions.

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