The Japanese press has taken to calling it sekkusu shinai shokogun: celibacy syndrome.
Basically, the country just isn't that interested in sex — and it could have huge effects beyond its borders.
The most recent evidence comes in a survey by the Japan Family Planning Association, reported on in the Japan Times.
A full 49.3% of respondents between the ages of 16 and 49 in the 1,134-person survey said they hadn't had sex in the past month.
There was a minor gender variation:
• 48.3% of men reported not having sex
• 50.1% of women reported not having sex
According to Japan Times, both figures showed a 5% increase since two years ago.
Respondents gave a range of reasons as to why: 21.3% of married men and 17.8% married women cited fatigue from work, and 23% of married women said sex was "bothersome." And 17.9% of male respondents said they had little interest (or a strong dislike) of sex.
Other research suggests even more extreme trends.
According to a 2011 report from Japan's population center cited by Max Fisher at The Washington Post:
• 27% of men and 23% of women aren't interested in a romantic relationship
• From ages 18 to 34, 61% of men and 49% of women aren't involved in a relationship
• From ages 18 to 34, 36% of men and 39% of women have never had sex
Experts say "the flight from human intimacy" in Japan comes from having a highly developed economy and high gender inequality. (According to the World Economic Forum, Japan ranks 104 out of 140 countries regarding gender equality, slotted between Armenia and the Maldives).
"Professional women are stuck in the middle of that contradiction," Fisher writes. "It's not just that day-care programs are scarce: Women who become pregnant or even just marry are so expected to quit work that they can come under enormous social pressure to do so and often find that career advancement becomes impossible. There's a word for married working women: oniyome, or 'devil wives.'"
That puts a squeeze on relational prospects for Japanese women. Fisher reports that women in their early 20s have a 25% chance of never marrying and a 40% chance of never having kids.
Japan's birth rate hit a record low in 2014 at just over 1 million infants. When combined with 1.3 million deaths in the same year, that's a deepening population crisis. According to Japan's population institute, the overall population could dip to 107 million by 2040 — or 20 million lower than today.
At the same time, Japan's population is shrinking and graying, setting up a "demographic time bomb" that could radiate out globally through the country's Greece-level national debt and deep economic ties with China and the US.
japanese old young menFlickr / St Stev
The Japanese government has stepped in to help with the national trend against relationships: Prime Minister Shinzo Abe's government wants 80% of fathers to take paternity leave, same as mothers taking maternity leave — while also increasing support for childcare. And one economist recommended a "tax on the handsome" to make geeky guys more attractive to women.
Different "demographic time bombs" are set to go off around the world: In China and India, the birthrates of boys have been outpacing those of girls for such a long time that a "marriage squeeze" is starting to hit both countries.