All Japanese could be surnamed Sato in 500 years, study predicts

In a striking prediction, Professor Hiroshi Yoshida of Tohoku University foresees a future where every Japanese citizen will share the same surname: Sato.

This projection suggests a dramatic shift in Japan’s societal fabric over the next five centuries. It is based on current social trends, cultural norms, and legal stipulations.

Yoshida’s research focuses on the impact of aging on society, and his findings indicate that the dominance of the surname Sato is already well underway.

As of March 2023, 1.529% of Japan’s people were named Sato, making it the most popular surname in the country, closely followed by Suzuki. This percentage rose by 0.83% from the previous year, influenced by marriages, divorces, births, and deaths.

Legal framework and cultural significance

In Japan , according to Article 750 of the Civil Code, married couples must use one surname, usually the husband’s. This rule reflects long-standing cultural traditions from Japan’s samurai times, where family lineage and property were passed down through the male line.

A major reason for this trend is Japan’s law that says married couples must have the same last name, as written in Article 750 of Japan’s Civil Code. This law, unique to Japan, mandates that nearly all couples adopt the husband’s surname.

In 2022, approximately 504,000 couples married, with 94.7% of them taking the husband’s family name. Consequently, the maiden names of around 478,000 women were effectively erased, leading to the gradual disappearance of some ancient family names, particularly in families where the daughter is an only child.

“This is very much part of the cultural heritage of the samurai era in Japan,” Yoshida explains, as reported by the South China Morning Post ( SCMP ).

“In the old days, only a man could be a samurai, and only his son could continue the family name, so women effectively did not have their own names.”

Despite the law allowing couples to choose the woman’s family name, deep-rooted cultural norms result in most couples opting for the husband’s surname. Yoshida attributes this to Japan’s slow progress in gender equality, noting that the country has never had a female prime minister.

The implications of a homogeneous surname society

Yoshida believes that if all Japanese people have the surname Sato in the future, it could cause problems. He thinks it would be inconvenient and make people feel less important. It might also make it harder to remember family and regional history.

He is part of the Think Name Project, a group dedicated to addressing the implications of the government’s refusal to allow women to retain their maiden names after marriage.

On International Women’s Day, March 8, the group, along with various businesses and social organizations, submitted a petition to the government seeking to amend the law.

However, despite past promises from Japan’s ruling Liberal Democratic Party to examine the issue, meaningful change seems unlikely. The party’s members are predominantly male, old, and deeply conservative, showing little real desire for reform.

As reported by SCMP , the influential Japanese Trade Union Confederation supports the push for change, with research indicating that more than 60% of people would prefer to keep their names after marriage or permit their spouse to do so if selective surnames were legally permitted.

Yoshida’s studies show that if more people were allowed to have different last names, only about 7.96% of Japanese might be named Sato by 2531. But even if this change happened, the name Sato would still become more common, and by 3310, everyone in Japan might have the last name Sato.

A demographic decline: Japan’s future population

Parallel to the surname study, Yoshida also conducted a demographic projection that paints a bleak picture of Japan’s future population. If Japan’s population continues to decrease as it is now, there would only be about 281,866 people in Japan by 2531 and just 22 people by 3310.

This dramatic decline implies that the Japanese population might disappear entirely before everyone adopts the surname Sato.

This combination of cultural traditions and a shrinking population brings attention to important problems in Japanese society. The possibility that everyone might have the same last name shows bigger issues with fairness between genders and how people see themselves in society. Also, the shrinking population means Japan needs to think about ways to keep its population steady in the long term.