Annual estimates of the levels and rates of victimization are derived by accumulating four quarterly estimates (which are not publicly available). The weights of all crimes reported during interviews in that year are summed, regardless of when the crime occurred. The base weight for personal crime is the sum of all person weights.
Series victimization is a category used when a respondent reports that six or more separate but similar victimizations have occurred during the 6-month reference period, but is unable to recall enough details of each incident to distinguish them from one another. Until recently, the NCVS estimates published in Criminal Victimization excluded series victimizations (or included them as a single victimization in certain special reports), which clearly undercounted the total number of all types of victimizations, including rape and sexual assault.
Beginning with Criminal Victimizations, 2011, BJS began including series victimizations directly in its estimates. The NCVS uses the victim’s report of the number of similar victimizations, with a maximum of 10, and collects (and applies to each victimization) detailed information only for the most recent victimization. These new procedures are being applied to all types of victimizations, including rape and sexual assault (Bureau of Justice Statistics, 2012a, p. 13):
BJS now includes series victimizations using the victim’s estimate of the number of times the victimizations occurred over the past 6 months, capping the number of victimizations within each series at a maximum of 10. This strategy for counting series victimizations balances the desire to estimate national rates and account for the experience of persons with repeat victimizations while noting that some estimation errors exist in the number of times these victimizations occurred. This bulletin is the first to include series victimizations throughout the entire report, and all victimizations estimates in this report reflect this new count strategy.
A technical report provides findings on the extent and nature of series victimization (Lauritsen et al., 2012, p. iii):
Including series victimizations in national rates results in rather large increases in the level of violent victimizations; however, trends in violence are generally similar regardless of whether series victimizations are included. The impact of including series victimizations may vary across years and crime types, in part reflecting the relative rarity of the offense type under consideration.