Japanese people could all be called Sato by 2531, study warns. But they'd need to get married first

Everyone in Japan could one day have the same surname unless its restrictive marriage laws change, according to a new study. But the country’s dwindling marriage rate could buck that trend and a rapidly declining population might render it moot entirely.

Everyone in Japan could one day have the same surname unless its restrictive marriage laws change, according to a new study. But the country’s dwindling marriage rate could buck that trend and a rapidly declining population might render it moot entirely.

Unlike most of the world’s major economies that have done away with the tradition, Japan still legally requires married couples to share the same surname. Normally, wives take their husband’s name – and same-sex marriages still aren’t legal in Japan.

A movement to change the rules around surnames has been brewing, led by women’s rights advocates and those trying to preserve the diversity of the Japanese surnames in a nation where a handful of names are becoming increasingly common.

If the rules carry on, all Japanese people could have the surname Sato by 2531, according to Hiroshi Yoshida, an economist from Tohoku University in Sendai, who led the study.

According to Myoji Yurai, a company that tracks Japan’s more than 300,000 surnames, Sato is currently the most common, followed by Suzuki. Takahashi comes third. About 1.8 million people out of Japan’s 125 million population have the surname Sato, Myoji Yurai says on its website.

Yoshida – whose family name ranks 11th most common – was commissioned by the “Think Name Project”, a group demanding legal changes to allow couples to keep both their last names.

The professor, who unveiled his latest study on Monday, conceded that his projection would only hold up if the country could overcome what is already one of its most pressing crises: an ever-declining marriage rate.