"The Bureau of Justice Statistics' (BJS) National Crime Victimization Survey (NCVS) is an annual data collection designed to gather information about nonfatal personal crimes and household property crimes in the United States. The main purpose of the NCVS is to accurately measure the number and type of criminal victimizations that occur each year to persons age 12 or older. Victimization rates are most commonly used in NCVS reports to describe changes in the level of personal and household crime over time and the levels of crime experienced by different population subgroups. However, prevalence rates also may be used to describe changes in the level of crime over time and differences between subgroups. This report discusses victimization rates and prevalence rates and the value of each type of indicator for understanding criminal victimization. Using NCVS data, the report displays and compares trends in the victimization and prevalence rates from 1993 to 2010. It also analyzes the differences between victimization and prevalence rates for various types of crime and demographic groups using data from the 2010 NCVS."
U.S. Bureau of Justice Statistics: http://www.bjs.gov/