Every Japanese Will Have Surname Sato by 2531 Unless Marriage Law Changed

A new study by Professor Hiroshi Yoshida of Tohoku University projects that if Japan continues requiring married couples to take the same surname, every single Japanese person will be named “Sato” by the year 2531.

The Sato Surname Explosion

Sato is already the most common surname in Japan, shared by 1.5% of the population as of 2023. Yoshida’s calculations show that between 2022 and 2023, the proportion of Japanese with the Sato surname increased by a factor of 1.0083. Assuming this growth rate remains constant, over 50% of Japanese will be Satos by 2446, increasing to 100% by 2531.

The Push for Surname Freedom

Yoshida conducted the study on behalf of the Think Name Project, a group advocating to legalize selective separate surnames for married couples. Currently, Japan legally requires spouses to take either the husband’s or wife’s surname upon marriage, with the wife taking the husband’s name in about 95% of cases.

Activist groups argue the century-old law, dating back to 1898, is outdated and discriminatory. They say it presents difficulties for women maintaining their professional identities and careers post-marriage. Allowing couples the freedom to keep their own names if desired would help address the issue.

Avoiding a “Nation of Satos”

Yoshida emphasized his surname projections are based on speculative assumptions to illustrate a point. “If everyone becomes Sato, we may have to be addressed by our first names or by numbers,” he commented to media. “I don’t think we can call that a good world to live in.”

He argues a nation where everyone shares the same family name would be highly inconvenient and “undermine individual dignity.” It would also lead to the loss of family histories and regional heritage tied to less common surnames.

Separate Surnames Could Postpone Sato Takeover

The professor ran an alternative scenario based on a 2022 survey showing 39.3% of Japanese aged 20-59 would want to keep the same marital surname even if given the choice. Assuming the surname law changed, he projected only 7.96% of Japanese would be named Sato by 2531.

In this case, the 100% Sato saturation point would be delayed until around the year 3310. By then, Japan’s population is projected to dwindle to just 22 people total if current trends continue. So enabling separate surnames could preserve more diversity until names become a moot point.

Bringing Attention to the Issue

Some initially mistook the eyebrow-raising study, published in late March, for an April Fool’s Day joke. But Yoshida said he intended it to be thought-provoking and draw attention to the potential societal impacts of Japan’s singular surname requirement.

Conservative politicians have resisted reforming the surname law, arguing it would undermine family unity and create confusion for children. The government has made some small accommodations, allowing maiden names to be listed alongside married surnames on certain official documents. But Japan remains the only country still legally mandating a shared marital surname.

Activist groups hope Yoshida’s research will add urgency to their campaign by illustrating the surname singularity Japan faces on its current course. They aim to persuade leaders that updating the marriage law to enable surname choice is critical to avoid a looming “Sato-pocalypse.”

What People Are Saying

“As someone planning to keep my surname when I get married, I’m glad this study is bringing more attention to the issue. The current law is archaic and sexist. Let people decide for themselves!” – Yumi_Nakano_85

“This really puts things in perspective. I don’t want to live in a Japan where everyone is a Sato. There are so many surname origin stories and regional histories that would be lost. It’s time to change the law.” – Kenji_Matsumoto_72

“Maybe I should change my name to Sato now and get ahead of the curve! Kidding, but this research does make a compelling case for allowing couples to make their own surname choices. Family unity comes from love, not a name.” – Hiroki_Tanaka_91

“I think some are missing the point that this is more of a thought experiment than a literal prediction. The professor is just trying to show how allowing only one marital surname is unsustainable long-term. Reform is long overdue.” – Akiko_Yamada_80

“Wait, so my future grandkids might not get to be Kobayashis? And their classmates will all be named Sato? That’s wild to think about. guess I’m in favor of the surname freedom now. Thanks for raising awareness, Professor Yoshida!” – Daisuke_Kobayashi_68