It found a correlation between sex and income, with men in the lower income brackets up to 20 times less likely to have had sex by the age of 40.
By comparison, men who lived in bigger cities and had a permanent job were more likely to have had sex.
"Although the discussion around cause and effect becomes very complex when considering who becomes sexually experienced and who remains a virgin, we show that heterosexual inexperience is at least partly a socio-economic issue for men. Simply put, money talks," said Cyrus Ghaznavi, the lead author of the study.
But for Japanese women it's a different story — they're less likely to be virgins if they make less money. The researchers said this may be because they are married homemakers.
To an extent, this is a widespread issue. A Washington Post report from 2018 found that the number of Americans not having sex had reached an "all-time high".
But still, the number of virgins in Japan is unusual compared to much of the rest of the developed world.
The country has the world's most rapidly ageing population, and the current birthrate sits at just 1.44 children per woman — far below what is needed for the country to maintain its population.
This leaves a shrinking cohort of workers left to look after an increasingly elderly population, which adds a barrier to sex.
There are other theories as to why people in Japan aren't having sex, ranging from a notoriously gruelling working culture, and the socio-economic stress associated with that — to a culture that, despite its multibillion-dollar porn industry, is relatively puritanical about sex compared to the West.
It's also worth noting the research did not include LGBT or asexual people, and assumed that all married couples had had sex.
By comparison, Australian surveys suggest that the number of heterosexual virgins in their 30s sits between 1 and 5 per cent.
A 2016 national body+soul survey found that the city of Melbourne had the highest number of virgins over the age of 31 — at less than 4 per cent.
