Everyone in Japan will have the same surname by 2531 unless laws are changed to allow married couples to have different names, according to a new study.
Sato is the most popular family name in Japan, shared by 1.5% of the population.
The study, led by Hiroshi Yoshida, a professor at Tohoku University, projects that will rise to 100% in just over 500 years if there is no change to legislation which currently requires married couples to take either the husband or wife’s last name.
Prof Yoshida stressed his estimate was “mechanically calculated based on an assumed scenario”, according to Japanese newspaper The Mainichi.
But he added: “If everyone becomes Sato, we may have to be addressed by our first names or by numbers.
“I don’t think we can call that a good world to live in.”
According to the research, the proportion of Japanese named Sato increased 1.0083 times from 2022 to 2023.
If that rate remains constant – with no change to the law – half of the Japanese population will share that name in 2446, rising to 100% in 2531.
Prof Yoshida said everyone having the same surname “will not only be inconvenient but also undermine individual dignity,” according to Japanese newspaper Asahi Shimbun.
“This would also lead to the loss of family and regional heritage associated with surnames.”
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The study was commissioned by the Think Name Project and other organisations that want Japan’s laws to change so couples can choose to have different surnames.
Japan is the only country in the world that requires married couples to use the same name.
Under a scenario where couples were allowed to take different names, Prof Yoshida forecast 8% of people would be called Sato by 2531.
He modelled this on a 2022 survey by the Japanese Trade Union Confederation, which found 39.3% of respondents wanted to share a surname, even if they had the option of using separate ones.
