手法を比較

	Migration Flow Estimation from Stocks	Migration Effectiveness Index
分野	Migration Studies	Migration Studies
系統	Process / pipeline	Process / pipeline
提唱年	2013	2002
提唱者	Guy J. Abel; Guy J. Abel & Joel E. Cohen	Martin Bell and colleagues
種類	Demographic-accounting pipeline for deriving migration flows from stocks	Descriptive index of migration efficiency and impact
原典	Abel, G. J. (2013). Estimating Global Migration Flow Tables Using Place of Birth Data. Demographic Research, 28, 505-546.	Bell, M., Blake, M., Boyle, P., Duke-Williams, O., Rees, P., Stillwell, J., & Hugo, G. (2002). Cross-national comparison of internal migration: issues and measures. Journal of the Royal Statistical Society: Series A, 165(3), 435-464.
別名	Stock-to-Flow Migration Estimation, Demographic Accounting of Migrant Stocks, Flow-from-Stock Method, Abel Stock-Differencing Method	Migration Efficiency Index, Aggregate Net Migration Rate, ANMR, MEI
関連	3	3
概要	Migration flow estimation from stocks reconstructs the unobserved movement of people between countries from something that is observed: how many foreign-born residents each country holds, broken down by country of birth, at two points in time. Most countries report migrant stocks — the number of people living abroad by where they were born — far more reliably than they report flows, the year-by-year counts of who moved where. Guy Abel's 2013 method, refined in the Abel and Cohen 2019 release covering 200 countries, treats the change in these bilateral stock tables between two censuses as the net result of migration plus births and deaths, and solves for the smallest set of origin-to-destination flows that could have produced the observed change. The approach rests on demographic accounting: a stock at the end of a period equals the stock at the start, plus births into the group, minus deaths, plus arrivals, minus departures. By fixing the demographic margins and minimizing flows, it turns a fragmentary stock record into a complete, comparable flow table. This has become the standard way to build globally consistent five-year migration flow estimates where direct flow data simply do not exist.	The migration effectiveness index measures how efficiently the gross churning of people between regions actually redistributes population, by expressing net migration as a share of total migration turnover. Two regions can each exchange enormous numbers of migrants and yet end up with almost unchanged populations, because the inflows and outflows nearly cancel; the same net change could instead arise from a small, lopsided, highly directed flow. The effectiveness index distinguishes these cases: it runs from near zero, where gross flows are balanced and population is barely redistributed, toward one hundred, where migration is so one-directional that almost every move contributes to net change. Martin Bell and colleagues codified this measure in their influential 2002 framework for cross-national comparison of internal migration, alongside companion indices of overall migration intensity and the aggregate net migration rate, which combines intensity and effectiveness into a single summary of how much migration reshapes the settlement pattern. Together these indices form a standard toolkit for describing and comparing migration systems across countries and over time.