Currently, Sato is the most common surname in Japan. 1.5 percent of the population now has that surname, but according to research by economics professor Hiroshi Yoshida, that figure could increase faster and faster in the coming years. In 2023, there were already 0.8 percent more people with that surname than the year before.
According to Professor Yoshida, the main reason for this increase is a law requiring married couples to have the same surname. Almost all married women in Japan take their male spouse’s name. As a result, less common surnames can disappear more quickly. If only women are born in a family, the family name will no longer be passed on to the next generation. Families with a rare surname are therefore at risk of losing their name.
In addition, Japan has very low birth rates. The birth rate has been declining in Japan for eight years in a row. “If people have fewer descendants, they cannot pass on their surnames,” says Jan Latten, former chief demographer at Statistics Netherlands. Latten also indicates that there are regional differences. “If birth rates drop in a certain region, surnames may disappear from that area.”
Two models
Professor Yoshida has calculated two models: one where married couples must have the same surname, and one where both partners can keep their own surname.
If the name Sato continues to grow in the coming centuries while couples have to keep the same surname, half of Japan’s population will be called Sato in 2446. In 2531, everyone in the country would have the same last name. According to Yoshida, if the law on surnames were abolished, ‘only’ 8 percent of the population would bear the name Sato in 2531.
“If everyone’s name is Sato, then we should only be addressed by a first name, or by numbers,” Yoshida told the Japanese newspaper Mainichi. “I don’t think that’s desirable.”
The chance that Sato will really become the only surname in Japan is very small, says Jan Latten. “By then, Japan could again be an immigration country where many people come from outside, and then all kinds of new names will be added.” It is possible that many of today’s Japanese surnames are slowly becoming rarer.
Old law
Yoshida’s research comes at a time when there is a lot of discussion about surnames in Japan. Only 39 percent of unmarried Japanese would still want to take the name of their future partner. But they don’t have that freedom of choice.
Japan is the only country in the world where both partners must always have the same surname. This is due to a law from 1898, which has been challenged several times in the Japanese Supreme Court in recent years, but without success. The court ruled in 2015 that the law is ‘deeply rooted in society’. That happened again in 2021.
Dutch surnames
In the Netherlands we also see that surnames change over time, says demographer Jan Latten. “The composition of the population is changing, some names disappear and others are added.” He indicates that immigration plays a major role in the Netherlands. “If you look at the composition of the population, the surnames in the Netherlands also have to change,” Latten explains.
“The native population is currently shrinking, and then you get a lot of other names from other countries. Then old Dutch names must become fewer. They no longer replace themselves, which means that you do not pass on your name.” Regional differences in the Netherlands also play a role. “We can expect names from the Bible Belt to survive longer than names from Limburg, where far fewer children are born,” says Latten.
There has been a campaign in Japan for years to change the law on surnames. Campaigners say this would increase gender equality in Japan, but some conservative politicians are against a change in the law. According to them, it would be at the expense of tradition and unity of families.
The law has a particular impact on women in Japan, as they typically take their husbands’ names. The Japanese newspaper Mainichi writes that more and more women are now using their maiden name at work, even if it differs from their legal name. The use of two surnames would regularly cause confusion, because women’s names on official documents often differ from the name they prefer to use.
Refused at hotel room
For example, Japanese businesswomen tell The Guardian that women are sometimes not allowed to enter their hotel room because the name on the booking does not match the name in their passport. “And for career women, changing their name is a denial of what they have achieved,” labor economist Machiko Osawa told The Guardian.
Japanese Prime Minister Kishida says the country must be careful with the law surrounding surnames. According to him, there is not yet broad support for change, and so the law appears to remain in force for the time being. As a result, many Japanese women continue to take their male husband’s name, and the percentage of Japanese with the surname Sato continues to grow.
