U.S. Department of Justice Office of Justice Programs Bureau of Justice Statistics ------------------------------------------------------ This file is text only without graphics and many of the tables. A Zip archive of the tables in this report in spreadsheet format (.csv) and the full report including tables and graphics in .pdf format are available on BJS website at https://www.bjs.gov/index.cfm?ty=pbdetail&iid=6046 This report is one in a series. More recent editions may be available. To view a list of all reports in the series go to https://www.bjs.gov/index.cfm?ty=pbse&sid=22 ------------------------------------------------------ ******************* Special Report ******************* ********************************************** Repeat Violent Victimization, 2005-14 ********************************************** ****************************************************** Barbara A. Oudekerk, Ph.D., and Jennifer L. Truman, Ph.D., BJS Statisticians ****************************************************** During the 10-year aggregate period 2005-14, an average of 3,249,900 persons age 12 or older experienced one or more nonfatal violent victimizations (rape or sexual assault, robbery, aggravated assault, and simple assault) during the year.*** Footnote 1 For offense definitions, see Criminal Victimization, 2015 (NCJ 250180, BJS web, October 2016) and Terms and Definitions: Victims (BJS web).*** The majority (81%) of victims experienced a single violent victimization during the year (figure 1).***Footnote 2 Unless otherwise noted, findings in this report are significant at the 95% confidence level.*** The remaining 19% experienced repeat violent victimization, defined as experiencing two or more violent victimizations during the year. More violent crime victims experienced two to five violent victimizations (14%) than six or more violent victimizations (5%). This report uses 1993 to 2014 data from the National Crime Victimization Survey (NCVS) to examine annual prevalence rates of nonfatal violent crime for persons age 12 or older who experienced a single or repeat (two or more) violent victimization. The majority of this report presents aggregate estimates for the 10-year period from 2005 to 2014 to describe the characteristics of repeat violent crime victims and the types of violent crimes they experienced during the year. Aggregating years increases the reliability and stability of estimates. ************************************************************* *********** HIGHLIGHTS ********** * The total nonfatal violent crime prevalence rate decreased 62% from 1993 to 2014, from 29.3 violent crime victims per 1,000 persons age 12 or older to 11.1 per 1,000. * In 2014, the prevalence of persons who experienced a single violent victimization (8.9 per 1,000) was 4.2 times higher than the rate of repeat violent victimization (2.1 per 1,000). * In 2014, the 5% of victims who experienced six or more violent victimizations accounted for more than a quarter (27%) of total violent victimizations that year. * During 2005-14, about 19% of violent crime victims experienced two or more violent victimizations per year. * During 2005-14, a greater percentage of intimate partner violence victims (33%) experienced repeat violent crime than victims of violence by other types of offenders. * During 2005-14, repeat violent crime victims experienced the majority of their victimizations by the same type of offender. * A greater percentage of rape or sexual assault victims (31%) experienced repeat violent crime during the year than victims of other crime types during 2005-14. * Among repeat violent crime victims who experienced at least one serious crime, most of the crimes committed against them were serious crimes. ************************************************************ ******************************************** Prevalence of repeat violent victimization decreased 62% from 1993 to 2014 ******************************************** From 1993 to 2014, the total nonfatal violent crime prevalence rate decreased 62%, from 29.3 violent crime victims per 1,000 persons age 12 or older in 1993 to 11.1 per 1,000 in 2014 (figure 2). The prevalence of victims who experienced a single violent victimization decreased 60%, from 22.4 victims per 1,000 in 1993 to 8.9 per 1,000 in 2014. Repeat violent victimization prevalence rates decreased 69%, from 6.9 per 1,000 in 1993 to 2.1 per 1,000 in 2014. From 2005 to 2014, total violent crime prevalence rates decreased 19%. This decrease was primarily driven by a 25% decline in the prevalence of victims who experienced a single violent victimization, from 11.8 victims per 1,000 persons age 12 or older in 2005 to 8.9 per 1,000 in 2014. The prevalence rate of repeat violent victimization did not change significantly from 2005 (1.9 victims per 1,000) to 2014 (2.1 per 1,000). For each year from 1993 to 2014, the majority of violent crime victims experienced a single violent victimization. In 1993, the prevalence of persons who experienced a single violent victimization (22.4 victims per 1,000 persons age 12 or older) was 3.3 times higher than the rate of repeat violence (6.9 per 1,000). In 2014, the rate of single violent victimization (8.9 per 1,000) was 4.2 times higher than the rate of repeat violent victimization (2.1 per 1,000). Prevalence rates for total, single, and repeat serious violent crime (rape or sexual assault, robbery, and aggravated assault) decreased from 1993 to 2014 (figure 3). In 1993, the serious violent crime prevalence rate was 12.6 victims per 1,000 persons age 12 or older, compared to 4.6 per 1,000 in 2014. The prevalence of victims who experienced a single serious violent victimization during the year declined 62%, from 10.6 victims per 1,000 in 1993 to 4.1 per 1,000 in 2014. Similarly, the rate of persons who experienced two or more serious violent victimizations declined 71%, from 2.0 per 1,000 in 1993 to 0.6 per 1,000 in 2014. From 2005 to 2014, there were no statistically significant changes in single or repeat serious violence prevalence rates. ************************************************************ ****************************************** Calculating prevalence rates for single and repeat violent victimization ******************************************* Prevalence rates measure the number of unique persons in a population who experienced at least one victimization during a specified period. Prevalence rates are estimated by dividing the number of victims in a specified population by the total number of persons in that population. Rates are multiplied by 1,000 to represent the number of victims per 1,000 persons in the population, or by 100 to represent the percentage of the population that experienced at least one victimization during the specified time (T). Prevalence rate per 1,000 personsT= (Number of victims in a specified populationT) divided by (Number of persons in the specified populationT) × 1,000 Percent of persons victimizedT = (Number of victims in a specified populationT) divided by (Number of persons in the specified populationT) X 100 This report presents data on the prevalence of violent victimization during the calendar year, including whether victims experienced a single or repeated violent victimization. Persons were repeat violent crime victims if they experienced two or more violent victimizations during the year, including victims who experienced high-frequency repeat victimization (six or more victimizations that were too similar in nature for the incidents to be distinguished from one another). For further information on calculating prevalence rates from the National Crime Victimization Survey data, see Measuring the Prevalence of Crime with the National Crime Victimization Survey (NCJ 241656, BJS web, September 2013). ************************************************************ ************************************************************ ********************************************** Time between first and second victimizations among repeat violent crime victims ********************************************** During 2005-14, the majority (96%) of repeat violent crime victims experienced their second victimization less than 6 months after their first victimization (table 1). More than half (56%) of repeat violent crime victims experienced their first two victimizations less than 1 month apart or as a high- frequency repeat victimization (i.e., series victimization). Series victimizations are similar in type but occur with such frequency that a victim is unable to recall each individual event or describe each event in detail. About 4% of repeat violent crime victims experienced their second violent victimization 6 months or more after their first violent victimization. ********************************************** In 2014, the 5% of victims who experienced six or more violent victimizations accounted for 27% of violent victimizations ********************************************** Repeat violent crime victims accounted for fewer than a quarter of the total violent crime victims each year from 1993 to 2014 (figure 4). The multiple victimizations that repeat victims experienced accounted for a disproportionate percentage of the total number of violent victimizations that occurred each year. In 1993, the 24% of violent crime victims who experienced repeat victimization accounted for 59% of the total violent victimizations committed against all persons age 12 or older that year. In 2014, of all violent crime victims, 19% were repeat violence victims and accounted for 50% of all violent victimizations. The concentration of victimizations was more pronounced among victims who experienced six or more violent crimes during the year. In 1993, the 8% of victims who experienced six or more violent victimizations accounted for 39% of all violent victimizations committed that year (figure 5). In comparison, the 5% of victims who experienced six or more violent victimizations in 2014 accounted for more than a quarter (27%) of total violent victimizations that year. ********************************************** During 2005-14, repeat violent crime prevalence rates were similar for males and females ********************************************** During 2005-14, a greater percentage of males (1.4%) than females (1.2%) experienced at least one violent victimization (table 2). This difference was due to a higher percentage of males (1.2%) than females (0.9%) who experienced a single violent victimization during the year. However, there was no significant difference in the percentage of males (0.2%) and females (0.2%) who experienced repeat violent victimization. During 2005-14, a greater percentage of persons ages 12 to 17 (2.4%) and 18 to 24 (2.2%) experienced at least one violent victimization than persons ages 25 to 34 (1.6%) and 35 or older (0.9%). This pattern across age groups was consistent with single violent victimization prevalence rates. The prevalence of repeat violent victimization was highest among persons ages 12 to 17 (0.5%) and lowest among persons age 35 or older (0.2%), compared to other age groups. A greater percentage of blacks (1.6%) experienced at least one violent victimization than whites (1.2%), Hispanics (1.3%), and other races (1.2%) during 2005-14. ***Footnote 3 White, black, and other race categories exclude persons of Hispanic or Latino origin*** These differences were primarily due to a higher prevalence of single violent victimization among blacks (1.4%) than persons of all other race and Hispanic origin categories. During 2005-14, a greater percentage of Hispanics (1.3%) experienced at least one violent victimization than whites (1.2%) (90% confidence level). This difference was due to a greater percentage of Hispanics (1.1%) experiencing single violent victimization than whites (1.0%). Hispanics had a higher prevalence of single violent victimization (1.1%) and a lower prevalence of repeat violent victimization (0.2%) than persons who identified as a race other than black or white (1.0% for single and 0.3% for repeat violent victimizations). ********************************************** A greater percentage of intimate partner violence victims experienced repeat violence than victims of violence by other types of offenders ********************************************** During 2005-14, the majority of violent crime victims experienced a single violent victimization during the year, regardless of the victim-offender relationship. Victims of intimate partner violence (IPV) experienced a greater percentage of repeat violent victimization (33%) than victims of violence committed by a well-known or casual acquaintance (26%), relative (25%), or stranger (17%) (table 3). Victims of violence committed by a stranger had the lowest percentage of repeat violent crime, compared to victims of violence by all other types of offenders. Examining the relationship between repeat victims and their offenders provides information about the diverse types of offenders committing violence against each victim. Repeat violent crime victims were more likely to experience two or more victimizations by the same type of offender than by different types of offenders. About a quarter (26%) of IPV victims experienced repeated violence by an intimate partner. Among victims of violence committed by a well-known or casual acquaintance, 19% were victimized at least twice by a well- known or casual acquaintance. An estimated 17% of victims of violence committed by a relative experienced repeat relative violence, and 11% of victims of violence committed by a stranger experienced repeat stranger violence. ********************************************** During 2005-14, a greater percentage of male than female victims experienced repeat victimization by a stranger ********************************************** On average per year during 2005-14, there were four times more female (298,100) than male (74,200) victims of IPV (table 4). However, a similar percentage of male (34%) and female (33%) victims of IPV experienced repeat violent victimization. Female victims of IPV (28%) were more likely (90% confidence level) than male victims of IPV (21%) to experience two or more violent victimizations committed by an intimate partner. During 2005-14, a greater percentage of female (27%) than male (20%) victims of relative violence experienced repeat violent victimization (90% confidence level). A greater percentage (90% confidence interval) of these female victims (19%) than male victims (13%) also experienced repeated violence by a relative. In comparison, during the same period there were more male victims (911,300) of stranger violence than female victims (509,000). A greater percentage of these male victims (12%) than female victims (9%) experienced repeat violent victimization committed by a stranger. ********************************************** During 2005-14, the 33% of IPV victims who experienced repeat violence accounted for 68% of all IPV victimizations ********************************************** During 2005-14, about 33% of IPV victims experienced repeat violent victimization during the year, and these victims accounted for more than two-thirds (68%) of all violent crime committed against IPV victims (figure 6). The percentage of all victimizations attributed to repeat victims was greater among victims of IPV (68%) than among victims of violence committed by well-known or casual acquaintances (repeat victims accounted for 58% of victimizations), relatives (56% of victimizations), or strangers (45% of victimizations). This was primarily driven by a greater percentage of IPV victims who experienced repeat violent victimization than those victimized by other types of offenders. On average among single and repeat violent crime victims, IPV victims (2.1) experienced a greater number of victimizations per victim than victims of acquaintance (1.7), relative (1.7, 90% confidence interval), or stranger (1.5) violence (appendix table 10). Repeat violent crime victims averaged about four victimizations regardless of the type of offender. ********************************************** Repeat violent crime victims experienced the majority of their victimizations by the same type of offender ********************************************** Examining the percentage of victimizations committed by each type of offender provides information about who committed the majority of violence against repeat victims. For example, a person who experienced four victimizations, three by an intimate partner and one by an acquaintance, is a repeat violent crime victim who experienced both IPV and acquaintance violence. However, the majority (75%) of these victimizations were committed by an intimate partner. During 2005-14, victims who experienced two or more violent crimes in a year experienced the majority of their victimizations by the same type of offender (table 5). An average annual 519,100 violent victimizations were committed against repeat violent crime victims who experienced at least one violent crime committed by an intimate partner. The majority of those victimizations were committed by intimate partners (88%), while a lower percentage was attributed to strangers (5%), well-known or casual acquaintances (4%), and relatives (2%). Similarly, of the 1,079,600 violent victimizations committed against repeat victims who experienced well-known or casual acquaintance violence, 85% were committed by a well-known or casual acquaintance during 2005-14. In comparison, 7% of these victimizations were committed by strangers, 3% by intimate partners, and 2% by relatives. Victims of relative violence who experienced repeat violent victimization experienced more violent victimizations by relatives (83%) than well-known or casual acquaintances (6%), intimate partners (5%), or strangers (4%). The majority (81%) of violent victimizations committed against victims of stranger violence who were repeat victims were also committed by strangers. Another 10% of these victimizations were committed by well-known or casual acquaintances, with a smaller percentage committed by intimate partners (3%) or relatives (2%). ********************************************** 31% of rape or sexual assault victims experienced repeat violent victimization ********************************************** During 2005-14, the majority of rape or sexual assault (69%), robbery (81%), aggravated assault (79%), and simple assault (77%) victims experienced a single violent victimization during the year (table 6). A greater percentage of rape or sexual assault victims (31%) experienced repeat violent victimization during the year than victims of robbery (19%), aggravated assault (21%), or simple assault (23%). In addition, a greater percentage of simple assault victims experienced two or more violent crimes during the year than robbery or aggravated assault (90% confidence level) victims. During this period, a greater percentage of rape or sexual assault (16%) victims experienced two or more rape or sexual assault victimizations than robbery victims who experienced repeated robbery (7%) and aggravated assault victims who experienced repeated aggravated assault (9%). More than half of repeat victims who experienced robbery (55%) or aggravated assault (56%) also experienced a simple assault, and 46% of repeat victims who experienced rape or sexual assault also experienced a simple assault (not shown). Among victims of simple assault, 19% experienced two or more simple assaults. ********************************************** During 2005-14, similar percentages of male and female victims of aggravated assault experienced repeat violent crime ********************************************** During 2005-14, on average per year, there were 6.8 times more female victims (135,800) of rape or sexual assault than male victims (20,100) (table 7). Among these victims, similar percentages of male (14%) and female (16%) victims experienced a second rape or sexual assault during the year. However, a greater percentage of male (45%) than female (29%) rape or sexual assault victims experienced two or more violent victimizations of any type during the year. During 2005-14, on average per year, more male victims (411,000) experienced at least one aggravated assault than female victims (278,400). Similar percentages of male and female victims of aggravated assault experienced any repeat violent victimization and repeated aggravated assault during the year. During the same period, there were more male (270,300) than female (159,300) robbery victims on average per year. A greater percentage (90% confidence level) of female (9%) than male (6%) robbery victims experienced repeat robbery during the year, and a greater percentage of female (24%) than male (16%) robbery victims experienced two or more total violent victimizations during the year. Similar percentages of male and female simple assault victims experienced repeat simple assault (18% of male and 20% of female victims) and repeat violent victimization (23% and 24%) during the year. ********************************************** Repeat victims accounted for a greater percentage of total victimizations among rape or sexual assault victims than victims of other crime types ********************************************** During 2005-14, the 31% of rape or sexual assault victims who experienced repeat violent victimization accounted for 67% of total victimizations committed against all rape or sexual assault victims (figure 7). Repeat victims accounted for a greater percentage of all victimizations among victims of rape or sexual assault (67%) than victims of simple assault (repeat victims accounted for 56% of victimizations), aggravated assault (51% of victimizations), or robbery (50% of victimizations). Repeat victims accounted for a greater percentage of victimizations among victims of simple assault (56%) than aggravated assault (51%) or robbery (50%). On average, rape or sexual assault victims experienced approximately 2.1 violent victimizations during the year, a higher number than robbery (1.6) or aggravated assault (1.6) victims (appendix table 14). Simple assault victims experienced an average annual 1.7 violent victimizations per victim. Among repeat violent crime victims, there were no statistically significant differences in the average number of violent victimizations per victim across those who experienced rape or sexual assault (4.5 victimizations per victim), robbery (4.3), aggravated assault (4.0), or simple assault (4.2). ********************************************** Violent crimes against repeat violent crime victims who experienced serious violence were most often the same type of crime or simple assault ********************************************** During 2005-14, of the victimizations committed against repeat violent crime victims who experienced aggravated assault, 61% were aggravated assault and 30% were simple assault (table 8). Rape or sexual assault accounted for an estimated 64% of the victimizations committed against repeat victims who experienced rape or sexual assault, followed by simple assault (26%). The majority of violent crimes committed against repeat violent crime victims who experienced robbery were robberies (60%) or simple assaults (31%). Among repeat violent crime victims who experienced at least one simple assault during the year, the majority (89%) of all victimizations committed against them were simple assaults. ************** Methodology ************** Survey coverage ***************** The National Crime Victimization Survey (NCVS) is an annual data collection conducted by the U.S. Census Bureau for the Bureau of Justice Statistics (BJS). The NCVS is a self-report survey in which interviewed persons are asked about the number and characteristics of victimizations experienced during the prior 6 months. The NCVS collects information on nonfatal personal crimes (rape or sexual assault, robbery, aggravated and simple assault, and personal larceny) and household property crimes (burglary, motor vehicle theft, and other theft) both reported and not reported to police. In addition to providing annual level and change estimates on criminal victimization, the NCVS is the primary source of information on the nature of criminal victimization incidents. Survey respondents provide information about themselves (e.g., sex, race, Hispanic origin, age, marital status, education level, and income) and whether they experienced a victimization. For each victimization incident, the NCVS collects information about the offender (e.g., sex, race, Hispanic origin, age, and victim-offender relationship), characteristics of the crime (including time and place of occurrence, use of weapons, nature of injury, and economic consequences), whether the crime was reported to police, reasons the crime was or was not reported, and victim experiences with the criminal justice system. The NCVS is administered to persons age 12 or older from a nationally representative sample of households in the United States. The NCVS defines a household as a group of persons who all reside at a sampled address. Persons are considered household members when the sampled address is their usual place of residence at the time of the interview and when they have no usual place of residence elsewhere. Once selected, households remain in the sample for 3 years, and eligible persons in these households are interviewed every 6 months either in person or over the phone for a total of seven interviews. All first interviews are conducted in person with subsequent interviews conducted either in person or by phone. New households rotate into the sample on an ongoing basis to replace outgoing households that have been in the sample for the 3-year period. Every 6 months, about a sixth of the sample rotates out of the study and is replaced by a new sample. The sample includes persons living in group quarters, such as dormitories, rooming houses, and religious group dwellings. It excludes persons living in military barracks and institutional settings, such as correctional or hospital facilities, and persons who are homeless. Nonresponse and weighting adjustments *************************************** In 2014, a total of 158,089 interviews were conducted with 104,721 persons age 12 or older for the NCVS. About 51% of persons were interviewed twice during the year. The response rate was 87% for eligible persons. Victimizations that occurred outside of the United States were excluded from this report. In 2014, less than 1% of the unweighted victimizations occurred outside of the United States. Estimates in this report use data from the 1993 to 2014 NCVS data files, weighted to produce annual prevalence estimates of victimization for persons age 12 or older living in U.S. households. Because the NCVS relies on a sample rather than a census of the entire U.S. population, weights are designed to inflate sample point estimates to known population totals and to compensate for survey nonresponse and other aspects of the sample design. The NCVS data files include weights for calculating various types of annual victimization estimates. Person weights were used in this report because they provide an estimate of the population represented by each unique person in the NCVS sample. Person weights allow for the calculation of annual prevalence rates, which estimate the number of unique persons age 12 or older who experienced victimization in a given year. Annual prevalence rates are calculated using information available from persons interviewed during the specified year. This report also presents the total number of victimizations committed against violent crime victims. Generally, BJS uses the victimization weight in the NCVS data files to produce victimization counts and rates. However, person weights are preferred when the analysis aims to count the number of unique victims or the number of victimizations experienced by unique persons, which is the purpose of this report. In addition, victimization weights are not designed to link individual victimizations to unique persons. Therefore, they are not appropriate for this report. With the victimization weights, the sample is adjusted to the full population for each 6-month period of the year. In comparison, the person weight adjusts the sample to the full population for the year, meaning that for each 6-month period, the weights essentially adjust the sample to half the population. Therefore, using the victimization weight to calculate the number of victims produces a higher prevalence estimate than using the person weight. It also may overestimate the number of victims because the same unique person can represent more victims than persons in the population per year. For technical details on how the victimization and person weights are constructed, see National Crime Victimization Survey Technical Documentation, NCJ 247252, BJS web, September 2014. The persons weights used in this analysis account for high- frequency repeat violent crimes (i.e., series victimizations). Series victimizations are similar in type but occur with such frequency that a victim is unable to recall each individual event or describe each event in detail. Survey procedures allow NCVS interviewers to identify and classify these similar victimizations as series victimizations and to collect detailed information on the most recent incident in the series. The weight counts series incidents as the actual number of incidents reported by the victim, up to a maximum of 10 incidents. Victims of series crimes were counted as repeat violent crime victims because they experienced more than one violent crime during the year. In 2014, about 5% of all victims and 25% of all repeat violent crime victims experienced at least one series victimization. For this report, person weights were used for all estimates of victimizations and victims. Person weights allowed BJS to examine of the number of victimizations accounted for by repeat violent crime victims and produce annual totals that represented the annual U.S. populations. Reporting a victimization in the NCVS *************************************** Some respondents had a reporting period of 6 months, while others reported on 1 year, depending on whether persons were surveyed in the NCVS once or twice in a given calendar year. All respondents reported on violent victimization that occurred during one 6-month period. About half of the sample was interviewed twice during each year. Some persons were interviewed once during the first half of the year because that was their last intended interview. Others may have moved out of a sampled household, or their second intended interview for that year was not obtained for some other reason. Some persons were interviewed once during the second half of the year because that was their first intended interview, they were persons recently moved into a currently sampled household, or they were missing a prior interview from the first half of the year for some other reason. Regardless of whether persons had one or two interviews during the calendar year, victimizations were summed. Using the NCVS person weights ensured that a person who experienced one or more nonfatal violent victimization within a 6-month period or in both 6-month periods in a given year was counted once in that annual prevalence estimate. An assumption underlying estimates of prevalence of repeat violent crime is that annual rates do not differ for persons who reported to the NCVS in one 6-month period from those who reported in both 6- month periods in a given calendar year. During 2005-14, the majority (96%) of all repeat violent crime victims experienced two violent victimizations in less than 6 months (see table 1). Among repeat violent crime victims who had a full year to report victimization during 2005-14, about 94% experienced their second victimization less than 6 months after their first victimization (table 9). In addition, rates did not differ significantly among persons with one interview compared to those with two interviews during the year for prevalence of violent crime (12.67 victims per 1,000 persons age 12 or older, compared to 12.75 per 1,000) or repeat violent crime (2.40 per 1,000, compared to 2.36 per 1,000) (table 10). The prevalence rates were driven by violence that occurred within a 6-month recall period. Therefore, a 6-month compared to 1-year reporting period does not significantly impact the estimates. Standard error computations ***************************** When national estimates are derived from a sample, as with the NCVS, caution should be used when comparing one estimate to another estimate or when comparing estimates over time. Although one estimate may be larger than another, estimates based on a sample are subject to sampling error. The sampling error of an estimate depends on several factors, including the amount of variation in the responses and the size of the sample. When the sampling error around an estimate is taken into account, the estimates that appear different may not be statistically different. One measure of the sampling error associated with an estimate is the standard error. The standard error can vary from one estimate to the next. Generally, an estimate with a small standard error provides a more reliable approximation of the true value than an estimate with a large standard error. Estimates with relatively large standard errors are associated with less precision and reliability and should be interpreted with caution. To generate standard errors around numbers and estimates from the NCVS, the U.S. Census Bureau produced generalized variance function (GVF) parameters for BJS. The GVFs take into account aspects of the NCVS's complex sample design and represent the curve fitted to a selection of individual standard errors based on the Jackknife Repeated Replication technique. The GVF parameters were used to generate standard errors for each point estimate (e.g., counts, percentages, and rates) in this report. BJS conducted tests to determine whether differences in estimated numbers, percentages, and rates in this report were statistically significant once sampling error was taken into account. All comparisons in the text were tested for significance. The primary test procedure was the Student’s t- statistic, which tests the difference between two sample estimates. Unless otherwise noted, the findings described in this report as higher, lower, or different passed a test at the 0.05 level of statistical significance (95% confidence level). Findings that passed a test at the 0.10 level of statistical significance are noted as such in the text (i.e., 90% confidence level). Caution is required when comparing estimates not explicitly discussed in this report. Data users can employ the estimates and the standard errors of the estimates provided in this report to generate a confidence interval around the estimate as a measure of the margin of error. The following example illustrates how standard errors can be used to generate confidence intervals: According to the NCVS, in 2014, the prevalence rate of violent crime among persons age 12 or older was 11.1 victims per 1,000 persons (see figure 2). Using the GVFs, it was determined that the estimated victimization rate has a standard error of 0.82 (see appendix table 2). A confidence interval around the estimate was generated by multiplying the standard errors by ±1.96 (the t-score of a normal, two- tailed distribution that excludes 2.5% at either end of the distribution). Therefore, the 95% confidence interval around the 11.1 estimate from 2014 is 11.1 ± (0.82 × 1.96) or (9.44 to 12.67). In other words, if the same sampling method was used to select different samples and computed an interval estimate for each sample for the population in 2014, the true population parameter (violent crime prevalence rate) would be expected to fall within the interval estimates 95% of the time. In this report, BJS also calculated a coefficient of variation (CV) for all estimates, representing the ratio of the standard error to the estimate. CVs provide a measure of reliability and a means for comparing the precision of estimates across measures with differing levels or metrics. Methodological changes to the NCVS in 2006 ******************************************** Methodological changes implemented in 2006 may have affected the crime estimates for that year to such an extent that they are not comparable to estimates from other years. Prior to 2006, first NCVS interviews were not included in the analysis and instead were used as a reference (bounding interview) for subsequent interviews. Beginning in 2006 and continuing through 2014, responses from households that were in the NCVS for the first time are included in the data. In this report, first interviews are included for 2006 to 2014 and the weights do not adjust for these unbounded interviews. Typically, these first interviews produce higher rates of victimization, but they represent a small portion of the total sample each year. The unbounded interviews contributed less than 0.1% to the total violent crime prevalence rates from 2006 to 2014. Evaluation of 2007 and later data from the NCVS conducted by BJS and the U.S. Census Bureau found a high degree of confidence that victimization estimates for years 2007 through 2014 are consistent with and comparable to estimates for 2005 and previous years. (For more information on changes to the NCVS in 2006, see Criminal Victimization, 2007 (NCJ 224390, BJS web, December 2008) and annual Criminal Victimization reports available on the BJS website.) ************************************************************** The Bureau of Justice Statistics (BJS) of the U.S. Department of Justice is the principal federal agency responsible for measuring crime, criminal victimization, criminal offenders, victims of crime, correlates of crime, and the operation of criminal and civil justice systems at the federal, state, tribal, and local levels. BJS collects, analyzes, and disseminates reliable and valid statistics on crime and justice systems in the United States, supports improvements to state and local criminal justice information systems, and participates with national and international organizations to develop and recommend national standards for justice statistics. Jeri M. Murlow is acting director. This report was written by Barbara A. Oudekerk and Jennifer L. Truman. Grace Kena and Jennifer L. Truman verified the report. Brigitte Coulton and Jill Thomas edited the report. Steve Grudziecki produced the report. August 2017, NCJ 250567 ************************************************************** *************************************************************** Office of Justice Programs Building Solutions * Supporting Communities * Advancing Justice www.ojp.usdoj.gov *************************************************************** *************************** 7/27/2017 JER 2:45pm ***************************