After analyzing the sexual activity of almost 10, people over almost two decades, scientists caught a glimpse of Americans' sex lives. According to a sweeping new study , men and women aged 25 to 34 years are having less sex — especially men. This is true regardless of sexual orientation. Overall, the research documents a rise in sexual inactivity between and On average, one in three men aged 18 to 24 years reported no sexual activity in the past year. The study, published Friday in the journal JAMA Network Open, documents a steady decline: In , 19 percent of men reported not having sex within a year. In , that increased to 31 percent of men.