Victimization is the basic unit of analysis used throughout this tool. A victimization refers to a single victim or household that experienced a crime. Crimes are distinguished from victimizations in that one crime may have multiple victims.
For violent crimes (rape or sexual assault, robbery, aggravated assault, and simple assault) and for personal larceny, the count of victimizations is the number of individuals who experienced a crime. For crimes against households (burglary, theft, and motor vehicle theft), each household affected by a crime is counted as a single victimization.
For violent victimizations, the victim, household, and incident characteristics included in this analysis tool are:
For property victimizations, the household characteristics included in the analysis tool are:
Estimates from the tool may differ from estimates in previous BJS publications that use NCVS data. This is because a small number of victimizations, referred to as series victimizations, are included in the analysis tool using a new counting strategy. High-frequency repeat victimizations, or series victimizations, are six or more similar but separate victimizations that occur with such frequency that the victim is unable to recall each individual event or describe each event in detail. BJS has decided to count series victimizations using the victim's estimate of the number of times the victimizations occurred over the past 6 months, capping the number within each series at a maximum of 10 victimizations. Including series victimizations in national estimates can substantially increase the number and rate of violent victimization; however, trends in violence are generally similar regardless of whether series victimizations are included. See Methods for Counting High-Frequency Repeat Victimizations in the National Crime Victimization Survey for further discussion of the new counting strategy and supporting research.
The NCVS is an annual data collection conducted by the U.S. Census Bureau for the Bureau of Justice Statistics (BJS). The NCVS collects information on nonfatal victimizations, reported and not reported to the police, against persons age 12 or older from a nationally representative sample of U.S. households.
The estimates presented in the tool are based on data gathered from residents living throughout the United States, including persons living in group quarters, such as dormitories, rooming houses, and religious group dwellings. Armed Forces personnel living in military barracks and institutionalized persons, such as correctional facility inmates, are not included in the scope of this survey.
Each housing unit selected for the NCVS remains in the sample for 3 years, with each of seven interviews taking place at 6-month intervals. An NCVS field representative's first interview with a household selected for the survey is conducted in person. The majority of follow-up interviews are conducted by telephone.
Collection and reporting of race and ethnicity data
In 1997 the Office of Management and Budget (OMB) introduced new guidelines for the collection and reporting of race and ethnicity data in government surveys. BJS implemented these methodological changes for all demographic surveys on January 1, 2003. BJS now allows individuals to choose more than one racial category. In prior years they were asked to select a single primary race. BJS now asks individuals whether they are of Hispanic ethnicity before asking about their race, and now asks people directly if they are Spanish, Hispanic, or Latino.
Accuracy of Estimates
The accuracy of an estimate is a measure of its total error, that is, the sum of all the errors affecting the estimate. This includes sampling error as well as nonsampling error.
BJS selects a sample from the entire population to use for the NCVS. BJS could have chosen from a large number of other possible samples of equal size that could have been obtained by using the same sample design and selection procedures. The estimates derived from any one of these samples would differ from one another due to sampling variability, or sampling error. Sampling error is often quantified with the standard error as described below.
In addition to sampling error, the estimates in this analysis tool are subject to nonsampling error. Sources of nonsampling error include nonresponse error, respondent recall error, poorly worded questions, interviewer and mode effects on response, and data entry error. While substantial care is taken in the NCVS to reduce the sources of nonsampling error throughout all the survey operations, by means of a quality assurance program, quality controls, operational controls, and error-correcting procedures, an unquantified amount of nonsampling error remains still. These nonsampling errors are difficult to measure.