Main contents start here
Outline of the Population Estimates
1 Purpose
Japan's population is grasped in detail through the Population Census every five years, Population Estimates are published in order to grasp population of every month and year for the intercensal period.
2 Contents
The estimates of "population by age (five-year groups) and sex for Japan" as of the first day of each month are published. The Bureau also releases the annual estimates of "population by age (single year) and sex for Japan" and "population by age (five-year groups) and sex for prefectures" as of October 1.
3 Method
1) Population as of the first day of each month is estimated by using the Census population as the base (the Base Population) and obtaining population changes during the intercensal period from other data sources.
2) Basic formula
| Estimated population= |
Base population |
* :For the Japanese and the Foreigners.
**:Only for the population by prefectures.
3) Sources
- Live births and Deaths------"Vital Statistics", Ministry of Health, Labour and Welfare
- Entries and Exits------"Statistics on Legal Migrants", Immigration Services Agency
- Net increase by change of nationality------The data of Ministry of Justice
- Inter-prefectural migrants------"Internal Migration in Japan Derived from the Basic Resident Registration", Statistics Bureau, Ministry of Internal Affairs and Communications
- Others------"Population Census", Statistics Bureau, Ministry of Internal Affairs and Communications
Please see below for the details.
The estimation method based on the 2020 Population Census.(PDF:149KB)
4 Revision of Method for Estimation
All Japanese migrants whose period of intended stay in foreign countries within 90 days (= the estimation by transients) has been included in the estimation of the migrational change, so it has a lot of seasonal fluctuation. We revised the method for the estimation by calculating Japanese exits of transients abroad every month and excluding them from Japanese migrational change, so as to change the Base Population from all Japanese migrants to "those who stay abroad for 91 days or longer". By this revision the Population Estimates become seasonally more stable. In the monthly report, the revised Population Estimates are released from January, 2007 (Provisional Estimates as of January 1, 2007, and Final Estimates as of August 1, 2006).
Additionally, the latest estimates are released one month later than current method because of the data availability. And the retroactively estimated results since October 1, 2003 are also released for reference.
Foreign migrants whose intended period of stay in Japan is less than three months have been excluded since the revision of the Immigration Control and Recognition Act in July 2012,and at the same time, Japanese transient migrants whose period of stay abroad is less than three months also became excluded.
5 Changing the Base Population
The Base Population of the Population Estimates is the one from the most recent Population Census. The Base Population is revised every time after the operation of the Population Census.
As the Population Census was conducted as of October 1, 2020, the Base Population of the Population Estimates has been based on the 2020 Population Census.
From December 2021, the Base Population of the Population Estimates is changed from the population by the 2015 Population Census to that by the 2020 Population Census tracing back to October 1, 2020.
6 Publication of results
1) Monthly Report and Annual Report
The estimates as of the first day of each month are published by the end of the stated month, as for the annual estimates of "population by age (single year) and sex for Japan" and "population by age (five-year groups) and sex for prefectures" as of October 1, in April.
2) Intercensal Adjustment
The population estimates between the previous Census and the next one of which final result is published have been revised by the intercensal adjustment and published.
Intercensal Adjustment of Current Population Estimates 2015-2020
(Notes)
Final estimates for the latest month's population will be computed 5 months later using updated sources.
Natural Change---As new figures are not available for the latest 2 months, the data of the previous year are used instead. Figures for the 3 and 4 months before the current month are based on the preliminary report.
Migration Change---As new figures are not available for the latest 5 months, the data of the previous year are used instead. All Japanse migrants whose period of stay in foreign countries within 90 days are excluded, and foreigner migrants whose period of intended stay in Japan within 90 days are excluded.
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