Changes in the Distribution of Sex Partners in the United States: 2002 to 2011-2013.

OBJECTIVE: The purpose of the current analysis is to examine subgroup differences in the distribution of opposite-sex sex partners in the United States across an approximate 10-year period to identify patterns that may inform sexually transmitted infection research and prevention. METHODS: Data were drawn from the 2002 and 2011-2013 National Survey of Family Growth, a US probability-based household survey focusing on sexual and reproductive health. The measures included in this analysis were lifetime opposite-sex sex partners and opposite-sex sex partners in the past year. Analyses were conducted separately for men and women. All analyses were conducted in R and R-studio with the "survey" package, focusing on medians, the 80th, and 95th quartile. RESULTS: In 2002, there were significant differences between men and women in median number of lifetime sex partners with men reporting more lifetime partners. However, in the 2011-2013 data, these differences are no longer significant. Still, the findings suggest that the top 20% and top 5% of men are reporting significantly more lifetime partners than their female counterparts. In comparison, partners in the past year remain relatively unchanged for both men and women. CONCLUSIONS: These findings suggest that there were important changes in the distribution of sex partners between 2002 and 2011-2013 that have implications for sexually transmitted infection prevention. Median lifetime partners are no longer different for women and men: however, the distribution of lifetime partners among men is becoming even more skewed.