WHEN Da Lin moved in with his girlfriend two years ago, his mother tried to stop them: she feared that their living together unmarried would sully his girlfriend’s reputation and, by association, his too. She will be happy only after they finally marry next year (his family is buying the apartment, hers the car). That generational clash is replicated in thousands of families across China: cohabitation without marriage was long anathema and officially illegal until 2001. Today it is commonplace. China’s social mores are changing astonishingly quickly. Before 1980 around 1% of couples lived together outside wedlock, but of those who wed between 2010 and 2012, more than 40% had done so, according to data from the 2010 and 2012 China Family Panel Studies, a vast household survey (see chart). Some reckon even that is an underestimate. A recent study by the China Association of Marriage and Family, an official body, found that nearly 60% of those born after 1985 moved in with their partner before tying the knot, which would put the cohabitation rate for young people on a par with that of America.

The number of unmarried couples living together is growing for many of the same reasons it has elsewhere: rising individualism, greater empowerment of women, the deferral of marriage and a decline in traditional taboos on pre-marital sex. Greater wealth helps—more couples can afford to live apart from their parents. Yet Chinese cohabitation has distinctive characteristics. In rich countries, living together is most common among poorer couples, but in China youngsters are more likely to move in together if they are highly educated and live in wealthy cities such as Beijing and Shanghai. Shacking up is seen as a sign of “innovative behaviour”, say Yu Xie of Princeton University and Yu Jia of the Chinese Academy of Social Sciences.

Elsewhere rising cohabitation represents the fraying of marriage: many couples never bother to wed. In China, however, cohabitation is almost always a prelude to marriage—as for Da Lin and his girlfriend—rather than an alternative to it. Marriage is still near-universal, although the skewed sex ratio resulting from China’s one-child policy and a cultural preference for boys has resulted in a surplus of poor rural men who will remain unhappily single. Some highly educated women in cities forgo marriage too.

In some Western countries those who live together for an extended period enjoy some of the same legal rights and obligations as married couples. In China cohabitation carries no legal weight. And it is very hard for a child born out of wedlock to acquire a hukou, or residency permit, which provides access to health care, education or other public services.

In the 1980s virginity was considered a woman’s chief asset and few couples dared to date openly, let alone live together. Now China is in the midst of a sexual revolution—some 70% of people have sex before marriage, according to a study conducted in 2012. Many young Chinese, however, still have conservative ideas about how their elders should behave: although cohabitation is also on the rise among the elderly, many of them avoid remarrying because their adult children oppose it.