China recorded a record-low birth rate of 6.77 births per 1,000 people last year, according to statistics released by China’s National Bureau of Statistics on Tuesday.

At the end of 2022, the country had 850,000 fewer people than it did at the end of the previous year. It is the first time the country has reached such a low number since the Great Famine, between 1959 and 1961.

This data is not a complete surprise as the country’s birth rate has been steadily declining for years. Shortly after the figures were released, Musk took to Twitter, writing: “Population collapse is an existential problem for humanity, not overpopulation!”

Musk was not directly referencing the data on China but it is not the first time he has spoken out about global birth rates. The tweet was in response to a 2018 tweet from the World Economic Forum that said: “Even as birth rates decline overpopulation remains a global challenge.”

Musk’s views on low fertility and low birth rates are long-standing. He believes that if birth rates do not rise, humanity will crumble, and often uses Twitter as a platform to express these concerns.

In August, the CEO tweeted: “Population collapse due to low birth rates is a much bigger risk to civilization than global warming…mark these words…(And I do think global warming is a major risk).”

Experts have said that these two issues are difficult to compare, however. But the recent low point count in China is of concern.

China used to be overpopulated. This triggered the country’s one-child policy in 1979. During this policy, many families were restricted to only being allowed one child.

This policy was then scrapped in 2016. But in recent years, China’s population has been going in the other direction.

However experts believe that the right policies will offset these concerns.

Stuart Gietel-Basten, professor of Social Science and Public Policy at the Hong Kong University of Science and Technology, told Newsweek: “It would only be concerning if nothing was being done to deal with the consequences—namely population stagnation and rapid ageing. Luckily, there are a lot of policies which have been put in place to offset some of these—especially around health, poverty reduction, developing social welfare systems, increasing productivity through, for instance, regional economic integration. Yes, it is certainly harder to sustain rapid growth under these new demographic circumstances, but it is by no means impossible.”

Demographer Yi Fuxian told Sky News that “China’s demographic and economic outlook is much bleaker than expected. China will have to adjust its social, economic, defense and foreign policies.”

China is not the only country that is recording a low birth rate. The United States recorded a birth rate of 11.06 births per 1,000 people in 2021. The U.S. birth rate has been declining since 2008.

The decline can be observed across many different demographics, making it somewhat of a mystery to experts. Births are down among women who are with and without college degrees, married and unmarried, and among different ethnicities.

Update 1/18/23 2:18 p.m ET: This article was updated to include comments from Stuart Gietel-Basten.