TOKYO. Around one in 10 Japanese in their thirties has never had heterosexual sex and the number of adults with no sexual experience is increasing, according to a new study based on national survey data.
Comparable data from other developed countries indicated that "Japanese adults tend to become sexually active later in life and that a substantially larger proportion remain heterosexually inexperienced into their thirties", the authors said.
The research is based on data from seven rounds of the National Fertility Survey of Japan, carried out between 1987 and 2015, which is administered by a unit overseen by the Japanese health ministry.
In 2015, 11.9 percent of women aged 30-34 and 12.7 percent of men in the same age group reported having had no heterosexual sexual experience, the data showed.
In the 35-39 age bracket, the figures were 8.9 percent for women and 9.5 percent for men.
In both age brackets, the number of self-reported virgins had increased by several percentage points from the earlier surveys conducted in 1987 or 1992.
Each round of the survey is administered to people aged 18-39 years old, and in total the researchers from the University of Tokyo found around a quarter of men and women in that demographic reported having never had heterosexual intercourse in 2015.
The survey data did not include information on same-sex intercourse.
But the authors said even assuming that five percent of respondents were engaged only in homosexual sex, "around one in twenty 30-39-year-old women and men ... would still lack sexual experience."
The study said Japan appears to be an outlier.
Data from the United States, for example, found just 1.9 percent of women aged 30-34 and 0.9 percent of women aged 35-39 reported no sexual partners of the opposite sex.
The figures for American men were just 3.1 percent for those aged 30-34 and 1.4 percent for those between 35 and 39.
The results are likely to be cause for concern given Japan's ongoing battle with population decline and a low fertility rate.
Japan's government has sought to tackle the problem by offering birth incentives and support for working mothers, including more nursery spots for young children.
"The situation of individuals who remain sexually inexperienced due to difficulties in finding a partner... maybe considered in future policies aimed at increasing Japan's birth rate," the authors wrote.
Peter Ueda, the study's lead author and an epidemiology expert at the University of Tokyo, said that "sexual inactivity or inexperience, whether voluntary or not, should not be exoticised, ridiculed or necessarily considered a concern for everyone."
"More research is needed on reasons for sexual inactivity and how mating market dynamics might be evolving," he added in a statement issued by the university.
The study said it found a correlation between sex and money, with men more likely to have had intercourse if they had permanent, full-time employment.
But they cautioned that cause-and-effect was difficult to determine on issues of sexual experience.
They also noted that while sexual activity might not be a priority for everyone, most respondents over 25 with no sexual experience reported hoping to get married, "indicating that their lack of sexual experience may be involuntary."
The researchers noted several potential limitations, including the self-reported nature of their underlying data.
And they pointed out that sexual inactivity could also be higher than their research suggests because they only examined whether respondents had any sexual history, not whether they were currently sexually active