In recent years, more and more Chinese couples are breaking with taboo and living together before marriage. Many couples are university students; others are youngsters undertaking so-called trial marriages. Even widowed elderly people are moving in together for care and companionship in their twilight years.

Researchers generally define nonmarital cohabitation as a sexual relationship in which the couple delays or forgoes the legal formalities of marriage. In 2001, the Chinese government removed a definition from the country’s marriage law that made it illegal for a man and a woman to live together outside of marriage. Today, the practice is only against the law when one or both cohabitants are already married to another person.

Between 2000 and 2010, about 20 percent of unmarried Chinese people aged 18 to 61 said they lived with their romantic partner. Cohabitation arrangements can be broken down into four types: premarital cohabitation, cohabitation with no intention of marriage, cohabitation in the aftermath of divorce or the death of a spouse, and illegal extramarital cohabitation.

Up to now, most studies have focused on premarital cohabitation among young people. This focus is based on the hypothesis that young people are more likely to cohabit outside of marriage. But in reality, the older an unmarried person is, the more likely they are to be in a live-in relationship. By 2015, the cohabitation rate among unmarried 18- to 29-year-olds was 52 percent, but among those aged 50 to 61, it was 89 percent. Presumably, this is due to the greater need for companionship and care as we begin to age.

People often mistake cohabitation arrangements for a kind of pre-wedding “trial marriage.” In reality, the percentage of currently cohabitating couples who intend to get married is actually quite low. According to renowned scholar Pan Suiming’s 2015 sexuality survey, 24 percent of unmarried respondents with live-in partners did not plan to marry their current partner, while another 35 percent said they didn’t know. Another 21 percent said there was “a possibility” that they would marry their current partner. Only around one-fifth of those with live-in partners reported that they were planning to tie the knot.

Although it is illegal for married individuals to live with someone of the opposite sex outside of the bonds of marriage, 3.5 percent of married respondents aged 18 to 61 reported doing so.

Compared with married people, those in nonmarital live-in relationships tend to be younger, more educated, higher earners, and only children. These couples generally socialize more than married people and have more friends of the opposite sex, although they are also more likely to say that others don’t find them attractive and that they don’t understand the sexual psychology of members of the opposite sex.

Unmarried cohabiting couples generally begin living together earlier than couples who end up getting married. Many also cohabit for comparatively short periods of time. They also report much lower levels of relationship satisfaction than married couples, generally feel less emotionally attached to their partners, and tend to argue more. Indeed, statistics show that unmarried Chinese couples have worse relationships than their married counterparts in almost every way, except for the quality of their sex lives, which they rate more highly than married individuals.

Researchers like to explain the rise in cohabitation in terms of Chinese society’s growing tolerance of live-in couples or the rising socio-economic costs of marriage. Others point to increasing social status for women and the erosion of the traditional moral conception of marriage, both of which dictate that adult men should take wives primarily to have children and carry on the family bloodline. We are told that all of this has made relationships more diverse and caused traditional marriages to lose their social importance.

While some of this analysis is compelling, it also helps to consider the topic from the perspective of individual choice. In China, most people see the ideal romantic relationship as one in which two people have sex, love each other, and are married. For Chinese adults, these three forces are the most important vehicles for finding meaning in life. Past research has shown that a person’s level of satisfaction with their sex lives, romantic lives, and marriages contributes more to their overall feelings of happiness than any other social, economic, or cultural factor, including physical health.

Sex, love, and marriage are related concepts, but they can also exist largely independent of one another: You can have sex without loving someone, love someone without being married, or be married and not have sex, for instance. But all three play a vital role in the lives of people of all cultures. So what should the relationships between them look like? Which of them should we emphasize most?

If sex, marriage, and love are key sources of happiness for most people, then it stands to reason that the ideal relationship is one in which you are able to maximize the potential of all three, so long as both parties remain respectful of one another’s individual wishes. Unfortunately, only about a third of Chinese people aged 18 to 61 reported having achieved all three. The remaining two-thirds tend to rank them in order of importance, and from there pursue one or two areas at the expense of others.

The core difference between unmarried live-in couples and their married counterparts is that the latter place greater importance on love and marriage, and less on a fulfilling sex life. Therefore, not only are they willing to get married, but their marriages are also marked by stronger emotional bonds. They might not have the best sex in the world, but to them, that’s OK.

Yet although unmarried cohabiting couples challenge traditional beliefs and lack the legal protections offered to married individuals, some of them are fine with this. They have happy sex lives, even if they miss out on some of the more fulfilling aspects of love and marriage.

Sex, love, and marriage are the building blocks of any romantic relationship; for many Chinese, you must strengthen all three if you want to be truly fulfilled. This unwritten understanding influences all sorts of social issues surrounding love and sex: Many Chinese people condemn the sex trade and extramarital sex partially because the pursuit of sexual satisfaction over love and conjugal happiness undermines the foundation of those building blocks: Lose one and you throw all three out of balance.

Live-in unmarried couples challenge tradition because they broadly reject the idea that fulfilling sex has to happen in the presence of love and marriage. In other words, not only can sex be kept relatively separate from love and marriage, it may even be better that way. We personally believe that this attitude is related to a rise in sexual hedonism among young Chinese people.

Our analysis indicates that the number of unmarried live-in couples will likely remain relatively constant in the near future. As a result, emerging attitudes toward sex, love, and marriage are unlikely to become mainstream, but will continue to be held by a sizeable minority. Indeed, in time the habits of cohabiting couples may form the building blocks for a diverse array of relationship types in years to come.

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