Over the past half century, rising individualism among Americans has coincided with ever loosening of attitudes toward sex relationships of all types. We've also seen an increasing number of lifetime sexual partners—except among Millennials. So say data derived from the General Social Survey, as reported in a new study by a team of psychologists. The survey, conducted almost annually by researchers at the University of Chicago, spans from 1972 to 2012 and covers some 57,000 participants. Reason Science Correspondent Ronald Bailey parses the data and reports, among other things, that between the 1970s and the 2010s, American adults became more accepting of premarital sex, adolescent sex, and same-sex sexual activity, but less accepting of extramarital sex.