[gibbonsrcool]

The decline in young people's sexual activity is a recent event: https://www.scientificamerican.com/article/people-have-been-...

[golemotron]

That started in Japan around 2000, a good ten years before the mental health crisis that struck kids at about 13 years of age in English speaking countries simultaneously.

[theGnuMe]

Japan is in some sense at the leading edge of male isolation and loneliness and depression.

[fomine3]

And limited internet access on feature phone (i-mode, J-Sky, EZweb) was a thing from around 2000. Many students had it. So it strengthen original argument.