that there was a decline in sexual frequency among married or cohabiting American adults from 1989-2014.Chateau Heartiste humbly suggests that the sex frequency declines
...American adults had sex about nine fewer times per year in the early 2010s compared to the late 1990s. This was partially due to the higher percentage of unpartnered individuals, who have sex less frequently on average. Sexual frequency declined among the partnered (married or living together) but stayed steady among the unpartnered, reducing the marital/partnered advantage for sexual frequency. Declines in sexual frequency were similar across gender, race, region, educational level, and work status and were largest among those in their 50s, those with school-age children, and those who did not watch pornography.
In analyses separating the effects of age, time period, and cohort, the decline was primarily due to the birth cohort (year of birth, also known as a generation). With age and time period controlled, those born in the 1930s (Silent generation) had sex the most often, whereas those born in the 1990s (Millennials and iGen) had sex the least often. The decline was not linked to longer working hours or increased pornography use. Age had a strong effect on sexual frequency: Americans in their 20s had sex an average of about 80 times per year, compared to about 20 times per year for those in their 60s. The results suggest that Americans are having sex less frequently due to two primary factors: An increasing number of individuals without a steady or marital partner and a decline in sexual frequency among those with partners.
primary causes are female obesity, female economic self-sufficiency, and the multigenerational drop in testosterone.
Female obesity: men are visually stimulated to bedroom action, and men really are disgusted by the sight of a female fatbody.
Female economic self-sufficiency: women are aroused by powerful men with resources to spare on them, and they are turned off by powerless cash-strapped men. Women who are in less need of a man’s resources are also less sexually interested in men who don’t make substantially more than they make (or have other compensating traits). If husbands’ incomes have decreased relative to wives’ incomes, then there will be a shift toward wives desiring less sex from their husbands. It’s biomechanics all the way down.
Testosterone decline: this one is self-evident. Lower T means lower libido, for men but also for women. Since men are the initiators of sex (especially within the confines of a long-term relationship), a low libido man will initiate less frequently, and his woman won’t take up the slack (women have a lot of pride in their ability to passively rouse their men to ardor, which is why they don’t like making the first move). If there’s lower T in women as well (a small amount of testosterone does affect female libido), then that would kill the passion just as quickly. Finally, low T men are just a plain turn-off to women. I have read studies which found women preferred the musky scent of sweaty shirts of men with high T.