State-by-state data on prison admissions from the National Corrections Reporting Program (NCRP) for 2003130 (the latest year with available data) were used to compute all the statistics in this report related to admissions to prison. In 2003, 35 states participated in the reporting of admission data to NCRP. The data were cleaned as follows before any analysis:
The NCRP database treats race and ethnicity separately, with one variable for race and one variable for ethnicity. We only used race in our analyses of prison admissions because of the large amount of missing data on ethnicity (23.8 percent cases with missing ethnicity). We recoded race into three categories: whites, blacks, and other. The other category includes cases for which the race was Indian American, Asian, Native Hawaiian, other, unknown, or blank cases. Each racial category can include Hispanics and non-Hispanics.
We used US Census Bureau projected population data for 2003132 to compute rates of admissions in this report. Rates were calculated per 100,000 adult (age 18 years or older) residents of the designated race and gender groups in each state for which we had drug admissions data. Races were recoded into three categories: white, black, and other, each of which may include Hispanics and non-Hispanics.
In the charts and figures in this report, unless otherwise specified, total frequencies and rates of admission were calculated on the basis of the total number of new drug admissions and the total populations for the 34 reporting states combined. The totals do not reflect averages.
The National Corrections Reporting Program does not provide data for all 50 states. In 2003, 35 states participated in the program (the number of participating states varies each year). The state of Alaska did not report any new prison admissions and we therefore excluded it from our analysis. The analysis presented in this report therefore is only valid for the 34 reporting states with new prison admissions. How the non-participating states differ in terms of drug admissions and racial disparity is unknown.
The reliability of the data contained in the NCRP database cannot be assessed.The NCRP database is based on a structured questionnaire completed annually on the basis of official prison records of prisoner population movement. After the questionnaires are processed by the Census Bureau, state tallies are sent to state officials for verification and comment. Limitations and information on data processing are provided in the codebook associated with the data.133
The NCRP database considers every prison admission as a new case. It is therefore possible that the same individual is represented more than once in the 2003 database if he or she was admitted more than once over the course of that year. However, since offenders are rarely sent to prison unless they have a sentence of one year or more, the possible number of duplicates among new prison admissions is unlikely to affect the analyses presented in this report.
Among the new drug offender admissions in the NCRP data base, 12.3 percent listed race as unknown, other or left the variable blank. There is no way of knowing whether or to what extent the results of our analyses would change had there been more complete reporting on race in the NCRP database.
130 Bureau of Justice Statistics (BJS), National Corrections Reporting Program Series, 2003, http://www.icpsr.umich.edu/cocoon/ICPSR/SERIES/00038.xml (accessed December 1, 2007).
131 BJS, Offense Code for the National Correction Program, ICPSR 20741 Codebook.
132 US Census Bureau, Population Estimates, March 2008, http://www.census.gov/popest/estimates.php (accessed April 16, 2008).
133 BJS, ICPSR 20741 Codebook.