In 500 years, everyone in Japan will have the surname ¡°Sato¡± if the current practice of requiring married couples to share the same last name continues, it has been forecast.

The simulation, organized by the Think Name Project and Asuniwa, was conducted by Hiroshi Yoshida, a Tohoku University economics professor with expertise in the graying of society, in a bid to show a possible future where separate surnames for married couples are not allowed. The project is a part of a campaign, designed to coincide with April Fools¡¯ Day, to raise awareness of the implications of not amending the law requiring married couples to share the same surname.

Everyone in Japan would have ¡°Sato¡± as their surname by 2531, the forecast found.

As of 2023, ¡°Sato¡± is the most common surname in Japan, used by 1.529% of the entire population. The annual growth rate of ¡°Sato¡± is assumed to be 1.0083%, based on the difference between 2022 and 2023 data

Starting from 1.530% in March 2023, with that yearly growth rate, the number of people with the surname would exceed 50% by 2446, the study said.

¡°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,¡± Yoshida said in a statement.

¡°Personally, I see changing one¡¯s name as a separate issue from getting married and living with one¡¯s partner. If we value individuality even more, there is no necessity to change one¡¯s name upon marriage,¡± he added.

The estimate was based on data from the website Myoji Yurai Net, which presents rankings of common surnames based on government statistics and telephone directory data.

Yoshida also calculated an alternative scenario in which married couples can have different surnames, revealing that everyone would have the surname ¡°Sato¡± by 3310 ¡ª delaying the possibility by around 750 years.

For this scenario, data from a survey conducted by the Japanese Trade Union Confederation in 2022, covering a thousand working men and women between the ages of 20 and 59, was used to calculate the result. The survey indicated that 39.3% of unmarried respondents preferred married couples to share the same family name if a selective surname system was introduced.

However, even if everyone having the same surname was delayed by around 750 years, the Japanese population may have become extinct by then due to the declining birth rate, the study noted. According to a study by the National Institute of Population and Social Security Research, the nation¡¯s population is estimated to be 281,866 people by 2531 ¡ª and 22 people by 3310.