Whole of Japan could have same surname by 2531

Everyone in Japan could have the surname “Sato” in about 500 years unless the law is changed that forces married couples to share a last name, a study has found.

“Sato”, meaning assistant or helper, is currently the most common surname in Japan, according to Prof Hiroshi Yoshida of Tohoku University.

More than 1.5 per cent of Japanese people held the name in 2023, and calculations show that the proportion increased 1.0083 times from 2022 to 2023.

If the growth continues at that rate, about half of the Japanese population will be named Sato in 2446, rising to 100 per cent in 2531.

The simulation was conducted in association with the Think Name Project, an initiative backed by several businesses supporting name diversity in Japan.

The initiative’s website shows examples of what Japan could look like if it maintains its shared surname policy – with coffee shops and businesses all named “Sato”.

That is, unless Japan adopts a selective surname policy and abolishes the current civil code implemented in the 1800s.

A 2022 study found that nearly 40 per cent of single people would choose to share a last name with their spouse if the policy was implemented, meaning only about 8 per cent would be named “Sato” by 2531, but the name would still take over by 3310.

“Considering that a family name has a family history and is also a cultural symbol, its loss would mean that the history of the family name would also cease to exist,” Mr Yoshida told The Japan Times.

Japan’s surname policy has come under increasing scrutiny of late with most people in favour of a selective policy.

According to a 2022 poll, 61 per cent of people favoured a selective policy, up from 50.5 per cent in 2018.

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

Japan is the only country in the world that requires spouses to share the same last name.

A class action lawsuit against the policy was filed by 12 plaintiffs earlier this month, contesting its constitutional grounding. Similar suits were filed in 2021 and 2015.

The justice ministry recommended a revision of the law as early as 1996.