Japan’s population is declining because deaths exceed births by more than migration from abroad offsets. Tokyo can keep growing because people also move within the country. These processes place different demands on government. Helping people have the children they want, attracting and retaining residents, and maintaining a bus or clinic in a shrinking community require different policies.
Fewer births explain the national decline
The scale of the birth–death gap is clear in the Statistics Bureau’s September 2026 population-estimates report. For the year from October 2024 through September 2025, it records about 694,000 births and 1.61 million deaths across the resident population. The natural decrease was about 919,000. Net international migration added about 336,000, leaving a decline of roughly 583,000 in that estimate series.
These annual flows explain the mechanism; they are not a decomposition of the five-year census loss. The report still uses the 2020 census base and says its estimates will be revised following the complete 2025 count. Keeping the periods and statistical bases separate avoids attributing a census revision to an abrupt wave of departures.
A low fertility rate matters, but so does the age structure inherited from earlier decades. The number of births depends on how many people reach childbearing ages as well as their fertility. A smaller cohort of potential parents can produce fewer births even if the average number of children per woman improves. Meanwhile, large older cohorts continue to reach ages with higher mortality. This is why a better year for births would not immediately stabilise the total population.
The National Institute of Population and Social Security Research projects population by age and sex using separate fertility, mortality and international-migration assumptions. Its projections are conditional paths, rather than a date on which the country is destined to disappear. Changing one assumption can improve the path without reversing all the pressures already embedded in the age structure.
The reasons people postpone marriage or plan fewer children deserve their own evidence. Our analysis of Japan’s low birth rate examines that household decision. Here, the immediate consequence is that a shrinking national total can persist while particular places attract more residents.
Moving to Tokyo changes the map
In 2025, the four-prefecture Tokyo area gained 123,534 residents through domestic migration, according to the resident-register migration report. That area comprises Tokyo, Kanagawa, Saitama and Chiba. Tokyo prefecture alone had a domestic net inflow of 65,219. These are moves within Japan, including Japanese and foreign residents, not arrivals from abroad.
A move into Tokyo removes a resident from another Japanese locality and adds one to the capital. It therefore helps explain Tokyo’s growth without increasing the national population. The consequences extend beyond the current headcount. A community losing working-age residents also loses some of the people who staff businesses, provide care and raise the next generation locally.
Net inflow does not tell us how many people are moving in each direction. In a 2026 paper in The Japanese Economic Review, economist Takeo Hoshi argues that the concentration debate gives too much weight to net movement while overlooking declining gross mobility. A place can remain a net destination even when the total volume of moves is falling. His exploratory relationship between mobility and growth is not proof that any relocation causes prosperity.
That distinction matters for policy. Preventing a departure can improve a town’s migration balance while leaving someone with a poor job match. A stronger local labour market would give that person a reason to stay and a choice of employers. Those are different achievements, even if both show up as one fewer outward move. A population target alone cannot tell a government which has happened.
Immigration is already cushioning the fall
Japan is not experiencing population decline in the absence of immigration. The same September report estimates 3.917 million foreign residents on 1 April 2026, around 301,000 more than a year earlier, while the Japanese-national population fell by about 860,000. Those detailed nationality figures refer to April, not the report’s provisional September headline. A change in the foreign-resident stock also includes births, deaths and nationality changes; it is not a count of new immigrants alone. The report separates those components.
The annual birth–death and migration figures above show the national constraint. Positive net migration reduces the loss, but at its recorded scale it does not offset the natural decrease. That does not make immigration ineffective. It means that slowing a decline and reversing it are different outcomes. Nor can a national inflow guarantee that a particular rural municipality will gain workers.
For a locality, attracting someone is only the beginning. A resident who can find another job nearby, secure suitable housing and build a life has more reason to remain than someone whose entire position depends on one employer. These are retention questions. They should be evaluated through actual staying, working and living conditions, rather than a national arrival total used as evidence that every regional labour shortage has been solved.
Growth can sit inside a declining prefecture
Tokyo prefecture and the wider Tokyo area are not interchangeable. The complete census places about 36.98 million people in the four-prefecture area, or 30.1% of Japan’s population, but its three surrounding prefectures all declined over the five-year period. Within the wider geography, Kawasaki, Saitama City and Chiba City gained residents while Yokohama lost them. The municipal results make the unevenness visible.
A prefectural average can conceal an expanding urban centre and a weakening outer area. It is therefore too broad a unit for deciding whether to open a school, add apartments or maintain a local transport link. The relevant population is the one that can actually reach and use the service. A growth label attached to a nearby city is not evidence that a settlement farther away has the same demand.
For anyone interpreting a housing or employment opportunity, this changes the useful question. Rather than relying on “Japan is shrinking” or “Tokyo is growing”, examine the particular municipality and neighbourhood, the age mix, employers and transport connections. The census identifies where to investigate; it does not provide a property valuation or establish that every employer in a growing city is expanding.
Fewer people do not remove every housing need
The census counted 57.18 million private households, up about 1.48 million from 2020, while their average size fell to 2.10 people. Tokyo’s average was 1.85. A household count measures something different from the number of residents: fewer people can be divided among more separate homes. The household results explain why population loss alone is an incomplete measure of housing demand.
That does not establish a shortage everywhere, or predict rents. It means a national stock of empty buildings cannot be treated as a ready supply for every household. Location, condition and the ability to use nearby services remain decisive. Our comparison of actual akiya offers shows how different the property bundle can be behind a low asking price.
For local government, the difficult cost is often the network connecting those homes. A road, water main or bus route does not automatically become proportionately shorter when the population along it falls. Maintaining broadly the same coverage spreads costs over fewer users. Reducing coverage can then make life harder for those who remain, particularly people who cannot readily drive or move.
Japan’s land ministry addresses this through compact-city planning linked to public transport. Its approach brings homes, medical and welfare facilities and shops into more accessible locations, coordinated with transport. The ministry also stresses cooperation between neighbouring municipalities. A service catchment can cross an administrative border even when each municipality maintains a separate population target.
The policy choice is who bears the adjustment
Concentrating services can make a clinic or bus network easier to sustain, but it can lengthen the journey for residents outside the chosen centres. Keeping facilities dispersed preserves proximity for some communities while spreading staff and maintenance budgets more thinly. Moving residents closer to services brings its own housing costs and disruption. Calling a plan “compact” does not settle those distributional questions.
One practical test is whether residents can still reach essential services after a change. Another is whether the plan funds the connections it assumes. A consolidated facility with a reliable transport link is a different offer from the same facility reached only by private car. These are criteria for judging a proposal, not a claim that every Japanese compact-city plan has achieved them.
The Tokyo Metropolitan Government disputes the argument that concentration in the capital is itself the principal cause of national decline. It points to natural decrease and to population gathering in regional centres as well. This is the capital’s stated policy position. Its defence of Tokyo should not be taken as evidence that outward movement imposes no costs on the communities people leave.
There is also a difference between managing an observed decline and claiming that one future is inevitable. A 2026 RIETI study by Tomoya Mori models continuing regional contraction and Tokyo concentration under a low-fertility, medium-mortality scenario. Its conclusions about household change, labour reallocation and real estate are tied to those assumptions. They help frame planning choices; they do not remove the need to examine a particular town’s prospects.
Hoshi’s economic analysis adds another caution: population and ageing alone do not explain Japan’s growth slowdown, and productivity matters greatly. That leaves room for better outcomes with fewer residents, but achieving them requires institutions and investment that improve how people work and live. A declining headcount is neither a complete diagnosis of economic performance nor an excuse to disregard the people facing a disappearing local service. The paper explicitly separates these mechanisms.
The latest census makes the task concrete. National policy has to address the birth–death gap and the conditions for long-term settlement. Regional policy has to decide how to maintain access as residents redistribute. Success in Tokyo does not carry out the second task for the rest of Japan. A credible response must show what improves for the people who stay, as well as count the people who arrive.
