Everyone in Japan will have the same surname by 2531, according to a simulation run at the Tohoku University research center.
Japan, where same-sex marriage is still illegal, currently requires couples to choose between their surnames when they get married. Ninety-six percent choose to go with the man’s name. According to Professor Hiroshi Yoshida at Tohoku University’s Research Center for Aging Economy and Society, if the law is not changed this will lead to a situation where every Japanese citizen will have the family name “Sato” in a little over 500 years.
As of 2023, Sato was the most popular surname in Japan, shared by 1.529 percent of the population. That seems low considering that the claim is that shouting “Sato” in 2531 Tokyo will result in just about every local citizen looking in your direction. However, the surname Sato grew by 1.0083 times from 2022 to 2023.
Continuing this growth rate (a huge assumption), everyone becomes Sato by 2531.
“From a general probability perspective, there are many cases of people marrying into a group with a major surname,” the paper explains, “and if this process is repeated over a long period of time, there is a possibility that they will be absorbed into the Sato surname and converge.”
If, however, Japan changes the law to allow for separate surnames, by that year only 7.96 percent of Japan’s citizens will be named Sato (assuming that 39.3 percent choose to continue to select one surname, the proportion of people who said they would do so in a 2022 survey). Under this scenario, we would still reach the Sato totality by 3310.
“However, according to ‘Japan’s Future Population Projections’ 2023.4, the Japanese population in 2120 is estimated to be 41,229,000. If this pace continues, the Japanese population is estimated to be 281,866 in 2,531 and 22 in 3310,” the paper adds. “In other words, even if 100 percent adoption of the Sato surname is postponed for 800 years, there is a high possibility that the Japanese people themselves will become extinct before that due to the declining birthrate.”
Of course, it’s probably not going to play out like that. The research was put together at the request of the Think Name Project, which aims to pressure the government into allowing married couples to have separate names, and was meant to highlight an absurd scenario if the law is not changed. Which is a shame for anybody who wants to know the surname of everybody in Japan, but only wants to learn one name.
[H/T: The Guardian]
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