This article is part of a series on gender and sexuality in China. Previous articles can be found here.

Many people think of China as a sexually repressed society. While this is true to some extent, the results of four nationwide surveys I led between 2000 and 2015 show that young Chinese people are becoming increasingly open about sex.

During those 15 years, the average age at which Chinese people reported having their first sexual encounter trended steadily downward. In 2000, sexually active men under age 30 lost their virginity at 22.6 years old on average. For women in the same group, the average was 21.7 years old. By 2015, these ages had dropped to 19.5 for men and 20.4 for women. These figures are highly significant: In just 15 years, men had their first sexual encounter a full three years earlier, and the age for women dropped by nearly a year and a half.

China’s consent laws criminalize all sex with girls under the age of 14. Although young Chinese people are having sex earlier and earlier, most still wait until adulthood to lose their virginity. In China, people can take on full-time work at 16 and are legally considered adults at 18. They also tend to have their first sexual experience later than people in Western countries.

The sex lives of the country’s university students also provide a glimpse into the changing sexual mores of young Chinese people. Over the past 20 years, the percentage of university students reporting to have had sexual intercourse has risen steadily, a trend that seems poised to continue. These percentages have increased at a similar rate for both men and women, but still fall short of the levels reported by Western college students.

University students are generally seen as being more open-minded than other groups. Yet our surveys reveal that, compared with other young Chinese, they remain more conservative in their attitudes toward sex. In fact, the percentage of university students who have had sex lags far behind that of their non-university-educated peers. University students are actually one of the more conservative communities in contemporary Chinese society.

Although the average age at which Chinese people first have sex has dropped, and the percentage of young Chinese engaging in sexual activity has risen, a contrasting trend has also emerged: There has been a noticeable rise in the number of people reporting lack of sexual interest.

During our surveys, we asked respondents whether they had felt uninterested in sex in the past 12 months. Among all men aged 18 to 29 years old, the percentage of those who said yes rose from 4.8 percent in 2000 to 12.1 percent in 2015. Among women, this figure rose from 12.8 percent to 27.3 percent in the same time frame. This is a truly surprising result: Not only are so many people losing interest while in their sexual prime, but their numbers have also more than doubled in the span of just 15 years.

There are doubtless many factors behind young Chinese people’s waning interest in sex, but I believe a particularly influential one is performance anxiety. Our survey also asked people if they had worried that their sexual performance would be inadequate or that they would be unable to satisfy their partner during sex at any point in the past 12 months. Among 18- to 29-year-olds, the number of men who said yes remained steady at around 48 percent, but the number of women who said they experienced anxiety jumped from just under 40 percent in 2000 to 64 percent in 2015.

In fact, there’s nothing strange about this. As sexual mores have become more open and information about sex has become more widespread, some people have unconsciously developed unreasonably high expectations of their own abilities in the bedroom. Such individuals often measure themselves against a supposed “ideal” when judging their own sexual performance. This, in turn, can easily become a source of anxiety or negativity. This is especially true as more and more Chinese people see sex as an equal act that should bring pleasure to both partners, a development that makes sexual satisfaction an important consideration and a source of worry.

To me, the correlation seems clear enough: An uptick in performance anxiety has led to declining interest in sex and, in turn, a decrease in overall sexual activity. Over the course of my study, many married or cohabitating 18- to 29-year-olds reported having sex less than once a month during the previous 12 months. While this rate held steady for men between 2000 and 2015, the number of women who reported having sex less than once a month rose by more than 11 percentage points in the same period.

It is important, too, to note the behavior of individuals who are celibate, whether voluntarily or not. It is widely known that gender imbalances have locked a number of men out of the marriage market, leaving them unable to find wives, lovers, or partners.

Most Chinese tend to refer to people who are still single at the age of 28 as daling weihun, or “older unmarried” youngsters. The following chart shows the percentage of men and women between the ages of 28 to 34 who were unmarried in each year of our study.

This chart not only reveals just how widespread this phenomenon is, but also shows that men are far more likely than women to remain unwed later in life. After the age of 30, there are far more unmarried men than unmarried women. Again, the reasons for this are numerous and varied. But I would like to make special mention of a phenomenon colloquially called “A-grade women and D-grade men.” China’s unmarried population is dominated by men from the lower rungs of society and women from its upper reaches, which makes it difficult for the two to pair off.

The proliferation of older unmarried youth is not purely the result of individual choice. More often, it is the result of class differences. This is especially true of men on the fringes of society — particularly rural men with low incomes — who often have difficulty finding a long-term partner. Given their social and financial circumstances, it is natural for them to experience periods of involuntary celibacy or infrequent sexual activity.

Young Chinese people have indeed grown more open when it comes to sex. But the real story lies in their emerging anxieties and the ways in which structural imbalances are leaving many young people unable to get married or find a live-in partner. Our data offers a snapshot of the complex attitudes and social phenomena that influence sex in contemporary Chinese society.

Translator: Kilian O’Donnell; editors: Lu Hua and Matthew Walsh.

Clarification: This article has been updated to clarify China’s laws on sexual consent.