noun
densely inhabited district; DID
Official statistical term used in Japanese censuses; often abbreviated as DID. Refers to an area with a population density of 4,000 or more per square kilometer.
国勢調査では、人口集中地区の人口が増加している。
In the national census, the population of densely inhabited districts is increasing.
市街地 is a general term for urban or built-up areas, while 人口集中地区 is a precise statistical definition used in official data.
Compound of 人口 (population), 集中 (concentration), and 地区 (district). A modern technical term with no historical derivation beyond its components.