As falling birth rates spread worldwide, smartphones and social media are emerging as a new key variable.

Gigazine reported on May 18 that recent declines are appearing simultaneously in developing countries as well as advanced economies, and that existing economic factors alone make it difficult to explain the sharp change.

More than two-thirds of countries worldwide are below the total fertility rate of 2.1 needed to maintain population. Japan's rate is expected to fall to around 1.13 in 2025, its lowest level on record. Mexico's birth rate in 2023 fell below that of the United States for the first time. Similar declines are also being seen in Brazil, Tunisia, Iran and Sri Lanka. The report stressed that as falling birth rates and population ageing progress together in low-income and middle-income countries as well, the trend is not limited to a specific region.

The key point is not the number of children that couples have, but that marriage and cohabitation are declining. In many high-income countries, including the United States, the number of children per woman who gives birth has held steady or even increased, but the share of women who give birth has fallen sharply. Another finding that differs from conventional wisdom is that declines in marriage and childbirth are more pronounced among lower-income and less-educated groups, not among higher-income groups.

Housing is also cited as an important factor. In the United States and Britain, rising home prices, falling homeownership rates and more young people living with their parents are intertwined with falling birth rates. Without a stable housing base, it is difficult to make long-term plans such as marriage and childbirth. The report also noted limits to explaining the global simultaneous decline with housing and the economy alone, as birth rates continued to fall even in relatively stable regions such as Northern Europe and in countries that were not hit hard by the financial crisis.

Against this backdrop, researchers are focusing on the spread of smartphones and social media. A research team at the University of Cincinnati said in a paper published in April that birth rates fell earlier and more steeply in areas where mobile internet spread quickly.

In the United States, Britain and Australia, birth rates clearly turned down around 2007. France and Poland did so around 2009, while Mexico, Morocco and Indonesia did so around 2012. Ghana, Nigeria and Senegal also saw a sharp drop between 2013 and 2015. It was commonly suggested that each turning point overlapped with the timing of smartphone adoption in those areas.

Experts point out that the digital environment has reduced face-to-face interaction and made it harder to find partners for dating and marriage. Another analysis says social media can distort benchmarks and raise expectations for forming relationships. Ultimately, smartphones and social media are emerging not as a simple technological shift but as a variable that changes the social structure around marriage and childbirth.