Photo/Illutration Tokyo's population in 2020 exceeded 14 million for the first time. (Asahi Shimbun file photo)

Only nine of Japan’s 47 prefectures have had population increases since 2015, a demographic trend that will lead to a significant reapportionment of Lower House seats, according to preliminary figures from the 2020 census.

The latest census was conducted in October 2020, and the preliminary results were released on June 25.

The Ministry of Internal Affairs and Communications said Japan’s total population in 2020 was 126,227,000, a decrease of 868,000, or 0.7 percent, over the 2015 census.

Tokyo’s population was 14,065,000, the first time the figure in the capital topped 14 million and representing a surge of 549,000 residents over the 2015 census, the largest increase for any prefecture.

The other eight prefectures that recorded population gains were Kanagawa, Saitama and Chiba, which all neighbor Tokyo, as well as Aichi, Fukuoka, Okinawa, Osaka and Shiga.

However, the increase in Shiga Prefecture was only 1,000, while Osaka Prefecture’s population rose by just 3,000.

The 38 prefectures that lost population were mainly rural areas. Hokkaido had the largest decrease at 153,000.

Population declines were also recorded in 1,416, or 82.4 percent, of Japan’s 1,719 municipalities. More than half of the municipalities saw their populations shrink by 5 percent or greater.

Lower House seats will be reapportioned from population-losing prefectures to five mainly urban prefectures--Tokyo and its three neighboring prefectures, as well as Aichi in central Japan.

Based on the preliminary census figures, 10 single-seat districts will be added to five prefectures, with Tokyo receiving five more seats, Kanagawa two more and one district each for Saitama, Chiba and Aichi.

The 10 prefectures that would lose Lower House seats are Miyagi, Fukushima, Niigata, Shiga, Wakayama, Okayama, Hiroshima, Yamaguchi, Ehime and Nagasaki.

There would also be reapportionment in the proportional representation constituencies, with the Tokyo bloc receiving two additional seats and the Minami-Kanto bloc getting one extra seat. The Tohoku, Hokuriku-Shinetsu and Chugoku blocs would lose one seat each.

The actual reapportionment procedure will be handled by a council under the internal affairs ministry and the new district lines drawn up over the course of a year, meaning the newly reapportioned seats will first be contested in the Lower House election to be held after 2022.

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