Why do rape victimization rates vary across studies? A meta-analysis examining moderating variables.

Research studies have identified multiple study- and sample-related factors that predict variation in the proportion of participants who report experiences of rape (non-consensual oral, anal, or vaginal penetration obtained by force, threat of force, and/or victim incapacitation). The magnitude of variation introduced by these methodological variables is often unclear, which can complicate attempts to compare findings across research studies. With the goal of identifying and quantifying sources of variation, we conducted a meta-analysis that compared rates of rape experienced by women in the United States during adolescence or adulthood. 6391 research articles were evaluated for inclusion and 84 studies (89 independent samples) met inclusion criteria. Results of a random-effects meta-analysis found that an average of 17.0 % (95 % CI [15.7 %, 18.3 %]) of participants across samples reported experiences of rape in adolescence or adulthood. The mean participant age, source of the sample, perpetration tactics included in the measure, and interaction between sample source and perpetration tactics each predicted significant variation in the proportion of victims identified. Participant recruitment method, publication year, and the earliest age included in the reference period did not predict significant variation. These findings clarify the impact of methodological variables on observed victimization rates and provide context that can inform comparisons across sexual victimization studies.