HONG KONG — Faced with a soaring divorce rate, the ruling Communist Party in China introduced a rule last year to keep unhappy marriages together by forcing couples to undergo a 30-day “cooling off” period before finalizing a divorce.

The rule appears to have worked, according to government statistics released this week, which show a steep drop in divorce filings in 2021.

Local officials have hailed the new rule as a success in the country’s effort to grow families and curb a demographic crisis threatening China’s economy. But the party has a much bigger challenge to reckon with: Fewer and fewer Chinese citizens are getting married in the first place.

Along with the decline in the divorce rate, the number of marriage registrations plunged to a 36-year low in 2021. The fall in marriages has contributed to a plummet in birthrates, a worrying sign in China’s rapidly graying society and a phenomenon more familiar in countries like Japan and South Korea.

Many young Chinese people say they would prefer not to get married, as a job becomes harder to find, competition more fierce and the cost of living less manageable.

“I do not want to get married at all,” said Yao Xing, a 32-year-old bachelor who lives in the city of Dandong, near China’s border with North Korea. His parents are pressuring him to get married and have children, but Mr. Yao said his job buying and selling kitchenware had made it hard to keep a steady income, which he sees as a prerequisite to marriage. Besides, he added, many women don’t want to get married anyway.

“I think more and more people around me don’t want to get married, and the divorce rate and marriage rate in China have dropped significantly, which I think is an irreversible trend,” Mr. Yao said.

Rising gender inequality at work and at home has caused many women to think twice about marriage as well. Better educated and more financially independent than their mothers, younger women have watched as their economic position has changed while society’s view of them has not.

“We call this a package deal, where a woman is not just marrying a man but the whole family,” said Wei-Jun Jean Yeung, a provost chair professor and founding director of the Center for Family and Population Research at the National University of Singapore. “This package does not seem to be a good deal anymore.”

The couples who do get married in China often prefer not to have children, citing worries about the rising cost of education and the burden of taking care of aging parents while also having young children. Some are delaying getting married, choosing instead to live together without the ceremony and, often, without the children.

“The relatively lower marriage rates coupled with rising divorce rates might signal the deinstitutionalization of marriage, which means more people might choose cohabitation over marriage,” said Ye Liu, a senior lecturer in the department of international development at King’s College London.

Fearful of the day when the population might begin to shrink, the Chinese government has spent years introducing policies to encourage marriage and having children. It has revised strict family planning rules twice in the last decade, first by ending a decades-old “one child” policy in 2015, and later by allowing married couples to have three children.

Officials have promised better maternity leave and protections for working mothers, though many pregnant women still report discrimination in the work force. Some cities have tried incentives like marriage leave, which gives newlyweds extra vacation days, to encourage couples to get married and start a family.

Despite these efforts, marriage rates have fallen every year since 2014. Around 7.6 million people got married in 2021, the lowest figure since officials started recording marriages in 1986, according to China’s Ministry of Civil Affairs.

Worried that married couples were moving too quickly to end their relationships, officials put in place a divorce “cooling off” period in January last year. The rule required couples to wait 30 days after filing for a divorce to continue with divorce proceedings.

“Some of the past divorce cases are impulsive divorces,” Dong Yuzheng, a population expert and president of Guangdong Academy of Population Development, told Chinese state media this week.

“Some people often quarrel when they encounter a trivial matter, and the so-called lack of common language is actually the result of the incorrect attitude of both parties, who do not put themselves in the right position and want to divorce impulsively when their emotions come up,” Mr. Dong said.

Chinese officials and academics like Mr. Dong have credited the cooling-off period for helping to slow the divorce rate. Officials said 2.1 million couples successfully completed divorce registrations in 2021, a 43 percent decline from 3.7 million in 2020.

Other experts say additional factors may have been at play. Ethan Michelson, an expert on Chinese marriage law and gender inequality at Indiana University, said the drop in the divorce rate might have to do with the difficulty of scheduling divorce appointments in the pandemic.

The data reported by the government is limited to what is known as “divorces by agreement,” which are processed by civil affairs bureaus and not by courts, where lengthy legal battles can occur. In the types of cases reported, spouses are required to apply jointly in person for divorce. After the 30-day cooling off, the couple must return or the divorce application is withdrawn.

Lockdowns and social distancing rules made the logistics of that process more difficult. There were also indications that the demand for divorce remained strong. In the three months before Chinese officials introduced the cooling-down period, people rushed to get divorced. More than a million filings were made, a 13 percent increase from a year earlier. And as state media trumpeted the slowing divorce rate this week, many Chinese people took to the internet to cast doubt on the news.

On Weibo, a popular Chinese social media platform similar to Twitter, a discussion around the new data was read by more than 310 million people. Many of the comments were disparaging. One commentator asked: “How many people don’t get divorced because they can’t? And the number of marriages is the lowest in 36 years.” Another person asked, “Why should we get married?”

Others were concerned about the consequences for victims of domestic violence. Rights activists have warned that the cooling-off rule is detrimental to people living in abusive marriages. Officials have countered that argument by claiming victims of domestic violence can ask the court to dissolve their marriages. But many victims, as well as stay-at-home mothers, do not have an income to pay for their own legal fees.

The overall message to women in China has been overwhelmingly negative, said Mr. Michelson, the professor at Indiana University and the author of an upcoming book on divorce in China. “Women are learning that if they get married they are risking losing everything,” he said. “They are risking their freedom to get out of a marriage.”

Liu Yi contributed research.