April 24, 2018
Population Estimates of Forced Intercourse
The frequent occurrence of sexual assaults on college campuses has focused national attention on this important public health concern, with estimates of sexual assault rates as high as 20% reported for undergraduate women. However, an important knowledge gap exists regarding rates of sexual assault for young adults in general, in that accurate population-based prevalence rates for both women and men who do and do not attend college are not readily available.
In a recent study, SRC Research Professor William Axinn, SRC Research Associate Professor Brady West, and recent MPSM Graduate Maura Bardos aimed to address this knowledge gap by characterizing rates of forced sexual intercourse for individuals with different amounts of college education. Forced intercourse is an important subset of total sexual assaults that represents nearly half of all sexual assaults. Axinn and colleagues accounted for age and college attendance in their analyses and characterized types of force experienced with forced sexual intercourse. To derive population-based estimates for forced sexual intercourse, Axinn and colleagues utilized data from the U.S. National Survey of Family Growth (NSFG), which offers a nationally representative sample of approximately 5,000 U.S. women and men ages 15 – 44. Two cohorts (2002 and 2011-13) were included in this study to assess prevalence rates over time. The NSFG study focuses on family life, reproductive health, marriage and divorce. Methodologically, the NSFG is designed to reduce reporting bias by utilizing audio-computer assisted self-interviewing (ACASI) to provide privacy and immediate encryption about sensitive information.
Axinn and colleagues estimated that approximately 20% of U.S. women aged 18-44 have ever been forced to have vaginal intercourse, which is similar to rates of sexual assault reported in college campus populations. Estimates of forced sexual assault increased with age, which may reflect increased exposure to risk with time. By the age of 44, approximately one in four women reported an experience of forced sexual intercourse, according to the study estimates. Lifetime estimates were generally lower for men, with approximately 6.5% reporting ever having experienced forced sexual intercourse. Unlike the monotonic increase in assaults associated with age in women, the rates changed in both directions across age groups for men. In the decade between the two NSFG cohorts, rates remained relatively stable for both women and men.
Women and men with four or more years of college reported lower rates of forced sexual intercourse. Women with fewer than four years of college education had 2.5 times higher odds of ever experiencing forced sexual intercourse then individuals with four or more years of college. For men with less than four years of college, the odds of ever experiencing forced sexual intercourse were 4 times higher compared to men with four or more years of college education. These findings generally held when adjusting for covariates associated with selection into college education. For both women and men, verbal pressure or abuse was the most frequently cited type of force experienced during the sexual assault.
The estimated rates of forced sexual intercourse highlight that sexual assault is a clear public health concern for both women and men, and in the decade between NSFG assessments there is no evidence of a decline in prevalence. It should also be noted that total sexual assault rates in the population are likely higher than reported here, because NSFG estimates are based on lifetime experiences and reflect only one subtype type of sexual assault. This underscores the need for more research to further characterize the full range of sexual assaults and associated consequences. Given that the majority of U.S. adults do not complete four or more years of college education, it is critical to expand intervention research to consider the unique contextual factors associated with individuals not attending college since these adults are at the highest risk for experiencing sexual assault.
William Axinn, Maura Bardos, Brady West (2018). General population estimates of the association between college experience and the odds of forced intercourse. Social Science Research, 70:131-143.