Sato already tops the list of Japanese surnames, accounting for 1.5% of the total population, according to a March 2023 survey, with Suzuki a close second.

Some social media users wrongly assumed the study, first reported on Monday but published in March, was an April fools’ day prank, but Yoshida said he wanted it to give people pause for thought.

A nation of Satos “will not only be inconvenient but also undermine individual dignity,” he said, according to the Asahi Shimbun, adding that the trend would also lead to the loss of family and regional heritage.

According to Yoshida’s calculations, the proportion of Japanese named Sato increased 1.0083 times from 2022 to 2023. Assuming the rate remains constant and there is no change to the law on surnames, around half of the Japanese population will have that name in 2446, rising to 100% in 2531.

Couples in Japan have to choose which surname to share when they marry, but in 95% of cases, it is the woman who changes her name.

However, the picture would be different if Japan’s government submitted to growing pressure to allow married couples to use separate surnames.

The study contained an alternative scenario extrapolated from a 2022 survey by the Japanese Trade Union Confederation, in which 39.3% of 1,000 employees aged 20 to 59 said they wanted to share a surname even if they had the option of using separate ones.

Under those circumstances, Yoshida, whose study was was commissioned by the Think Name Project and other organisations that want to legalise the opportunity to select your surname, projected that by 2531, only 7.96% of the Japanese population would be named Sato, the Mainichi Shimbun reported.