Why Does Japan Have 47 Prefectures? | Data in Motion #02

About 150 years ago, Japan's population table listed 77 divisions. Watch them merge and split until there are 47, then follow the population race through the 2025 census. Japan's prefectures are a bit like states; the white labels inside each bar show which present-day prefectures the pieces belong to.

How the number of divisions changed

“Divisions” means the number of bars in the video. The 77 in 1872 include 75 prefectures, Hokkaido under the Kaitakushi (colonization office), and Ryukyu.

Start with the 40 divisions of summer 1876, add the eight restored prefectures—Tokushima, Fukui, Tottori, Toyama, Saga, Miyazaki, Nara and Kagawa—and subtract Sakai, which joined Osaka: 40 + 8 − 1 = 47. Hokkaido's change from one division to three and back to one has no net effect. Some prefectural boundaries changed afterward.

Comparing the Meiji-era leaders

These populations use the boundaries of the time. A familiar prefecture name does not necessarily mean its present-day area. Figures marked “about” are approximate.

The video's light-blue background marks the estimated period, 1876–1883. Without resident-population statistics for those years, bar lengths are estimated from the surrounding records. Osaka's lead in 1881–1883 is a result of that estimate. Counts based on where people's family registers were held put Niigata slightly ahead on January 1 in both 1882 and 1883. The pieces within each bar, showing today's prefectures, are also estimates. This episode contains no future projections.

Milestones in the race of 47

All figures below are in people. For readability, Tokyo and Hokkaido keep the same English labels across changes in their Japanese administrative names.

The Tama area moved from Kanagawa to Tokyo on April 1, 1893. Its population that day, about 230,000, and Tokyo's rank that day are estimates. The table instead compares the recorded year-end figures for 1892 and 1893.

Japan's first national census in 1920 changed the counting method used by earlier register-based statistics. The 1940 census counted soldiers overseas at their home address; the 1945 survey excluded people in military units, among others. Tokyo's recorded change from 1940 to 1945 was −52.6%, with those differences in survey coverage. Okinawa was outside the 1945 survey's coverage; its missing bar does not mean a population of zero.

What this episode shows

• Eight prefectures were restored after the count reached 40 in summer 1876; subtract Sakai's merger into Osaka, and the count reached 47 in December 1888.
• Mergers, separations and boundary transfers also changed population rankings; Hokkaido led in the November 1945 survey.
• Tokyo was the only prefecture whose population grew from 2020 to 2025; the other 46 declined.