Nagasaki長崎県
Saikai 西海市
Data last updated:
Saikai, Nagasaki, Japan has a population of 23,433 (2025 national census). IPSS projections estimate 20,934 by 2030 and 12,827 by 2050 (a decrease of about 51.2% from 2020), with the share of residents aged 65+ rising from 38.8% in 2020 to 50.4%.Sources: Japan Census (Statistics Bureau), IPSS Regional Population Projections (2023)
2025
(Census)
23,433
2030
(Projection)
20,934
▼ -20.3%
2040
(Projection)
16,641
▼ -36.7%
2050
(Projection)
12,827
▼ -51.2%
Change vs. 2020 census
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Other municipalities in Nagasaki (長崎県)
Data Sources
- Portal Site of Official Statistics of Japan (e-Stat)（https://www.e-stat.go.jp/）
- National Institute of Population and Social Security Research (IPSS), Regional Population Projections (2023 ed.)
* This service uses the e-Stat API but its content is not guaranteed by the Japanese government.
Saikai Population Table (1980–2050)
Population by year: national census results (restated to current municipal boundaries) and IPSS (2023) projections based on the 2020 census.
| Year | Population | vs 2020 | Type |
|---|---|---|---|
| 1980 | 41,064 | ▲ +56.3% | Census |
| 1985 | 39,670 | ▲ +51.0% | Census |
| 1990 | 37,610 | ▲ +43.1% | Census |
| 1995 | 36,327 | ▲ +38.3% | Census |
| 2000 | 35,288 | ▲ +34.3% | Census |
| 2005 | 33,680 | ▲ +28.2% | Census |
| 2010 | 31,176 | ▲ +18.7% | Census |
| 2015 | 28,691 | ▲ +9.2% | Census |
| 2020 | 26,275 | — | Census |
| 2025 | 23,433 | ▼ -10.8% | Census |
| 2030 | 20,934 | ▼ -20.3% | Projection |
| 2035 | 18,731 | ▼ -28.7% | Projection |
| 2040 | 16,641 | ▼ -36.7% | Projection |
| 2045 | 14,666 | ▼ -44.2% | Projection |
| 2050 | 12,827 | ▼ -51.2% | Projection |
About Saikai
Overview
Saikai (西海市) is a municipality in Nagasaki, Japan, with a population of 23,433 as of 2025.
Population Projection of Saikai
According to projections by Japan's National Institute of Population and Social Security Research (IPSS), Saikai's population is expected to reach 20,934 by 2030 (-20.3%), 16,641 by 2040 (-36.7%), and 12,827 by 2050 (-51.2%). The town is projected to lose more than half its population over 30 years.
Aging Rate of Saikai
The aging rate (percentage of residents aged 65 and over) is 38.8% as of 2020 and is projected to rise to 50.4% by 2050. More than half of residents will be seniors, placing the town in the "marginal municipality" category.
National Comparison
Saikai is experiencing one of the faster rates of population decline in Japan.
National and Prefectural Rank
- Population decline rate: Ranked #293 out of 1903 municipalities nationwide.
- Aging rate in 2050: Ranked #536 out of 1903 nationwide.
- Population size: Ranked #1017 out of 1917 nationwide.
- Related: National rankings / All municipalities in Nagasaki
Earnings in Nagasaki (長崎県): Average salary in Nagasaki (長崎県) by age, gender and company sizejpsalary / MHLW Basic Survey on Wage Structure