手法を比較

	Migrant Stock Estimation	Residual Method for Unauthorized Population
分野	Migration Studies	Migration Studies
系統	Process / pipeline	Process / pipeline
提唱年	1983	1987
提唱者	United Nations Population Division (standard measurement conventions)	Robert Warren and Jeffrey S. Passel
種類	Cross-source pipeline for counting the resident migrant population	Demographic-accounting estimation pipeline for unauthorized population
原典	United Nations (1983). Manual on Methods of Estimating Internal Migration (Manual VI). Population Studies No. 47. New York: United Nations.	Warren, R., & Passel, J. S. (1987). A Count of the Uncountable: Estimates of Undocumented Aliens Counted in the 1980 United States Census. Demography, 24(3), 375-393.
別名	Foreign-Born Stock Estimation, International Migrant Stock, Migrant Population Counting, Stock-Based Migration Measurement	Demographic Residual Method, Warren-Passel Residual Method, Census-Minus-Legal Residual, Unauthorized Foreign-Born Residual
関連	3	3
概要	Migrant stock estimation answers a deceptively basic question: how many migrants are living in a place at a given moment? Unlike migration flows, which count moves over an interval, a stock is a cross-sectional count of people whose origin differs from their place of residence — most commonly the foreign-born, but sometimes the foreign-national or those who have lived abroad. The United Nations measurement conventions, set out in its migration manuals, fix the core definitions (place of birth versus citizenship, duration thresholds, usual residence) and the at-risk concepts that make stocks comparable. In practice the analyst rarely has one clean source: censuses give place-of-birth tables but miss recent or irregular arrivals, population registers give continuous citizenship-based counts but vary in how they handle departures, and surveys give detail but suffer sampling error. Migrant stock estimation is therefore a pipeline that compiles these sources, harmonizes their differing definitions and geographies, and adjusts for undercount, overstay, and double counting, drawing on the same comparability concerns Bell and colleagues raised for internal migration. The output — a coherent count of migrants by origin, age, and sex — underpins integration policy, flow estimation, and the denominators of countless migration indicators.	The residual method estimates the size of the unauthorized migrant population by subtraction: it takes the total foreign-born population counted in a census or large survey and removes the part that can be accounted for as legally resident, treating whatever remains as the unauthorized residual. Robert Warren and Jeffrey Passel introduced and validated the approach in their landmark 1987 Demography article, which matched undocumented aliens counted in the 1980 United States census against administrative records of legal immigrants. The arithmetic is deceptively simple, but the credibility of the estimate lives entirely in the adjustments. The legally resident stock must be aged forward from admission records and reduced for those who have since died or emigrated, and the resulting residual must be inflated to account for the share of unauthorized migrants the census itself failed to count. Done carefully and computed within detailed demographic cells — by age, sex, country of birth, and period of entry — the method turns two imperfect data sources that each say nothing directly about legal status into a defensible national estimate. It remains the dominant approach used by United States statistical agencies and research centers to size the unauthorized population.