The latest census, carried out in October, shows Japan's population at 126.92 million, up 1.35 million from five years ago, the Management and Coordination Agency said Friday, noting that the corresponding growth rate of 1.1 percent was the lowest in the postwar era.
The increase was far smaller than the 1.6 percent in the previous summary census taken in 1995, reflecting the rapid aging of the society and the declining birthrate, the agency said in the preliminary report.
The census also has political implications, as single-seat constituencies for the Lower House will have to be redrawn in 10 prefectures in light of demographic changes.
The Council on the House of Representatives Electoral District will discuss adding one Lower House seat each in Saitama, Chiba, Kanagawa, Shiga and Okinawa prefectures and reducing constituencies in Hokkaido, Yamagata, Shizuoka, Shimane and Oita prefectures.
It is expected to submit a revision plan to Prime Minister Yoshiro Mori within a year.
Census-takers found 62.10 million men and 64.82 million women in the country.
The number of households across Japan stood at 47.03 million, up 6.6 percent from 1995, while the number of family members per household stood at 2.7, down from 2.85.
Populations in 24 prefectures declined, the census shows.
Among them, Akita had the biggest loss, 2 percent. Shiga, meanwhile, had the largest gain, 4.3 percent.
The combined population of Tokyo's 23 wards also increased, reversing a 15-year trend of decline.
Tokyo, Osaka and Aichi prefectures accounted for 90 percent of the nation's overall population gain.
According to United Nations statistics, Japan accounted for 2.1 percent of the global population of 6.06 billion, but its rank dropped from eighth to ninth.
In light of the census result, discussions to redraw the Lower House constituencies in 10 prefectures will start Monday.