手法を比較

	Migration Effectiveness Index	Internal Migration Intensity Index
分野	Migration Studies	Migration Studies
系統	Process / pipeline	Process / pipeline
提唱年	2002	2002
提唱者	Martin Bell and colleagues	Martin Bell and colleagues (IMAGE programme)
種類	Descriptive index of migration efficiency and impact	Descriptive index of overall internal-migration propensity
原典	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.	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	Migration Efficiency Index, Aggregate Net Migration Rate, ANMR, MEI	Crude Migration Intensity, Aggregate Crude Migration Intensity, CMI / ACMI, Migration Intensity Measure
関連	3	3
概要	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.	The internal migration intensity index measures how much migration occurs within a country — the overall propensity of people to change their place of usual residence — independently of where they move or what the net redistribution is. Its simplest form, the Crude Migration Intensity (CMI), is just the number of internal migrants over an interval divided by the population at risk, expressed per hundred or per thousand. Martin Bell and colleagues, in their 2002 Journal of the Royal Statistical Society paper and the later IMAGE programme, showed that this apparently simple measure is treacherous to compare across countries because it depends heavily on how the territory is carved into zones: the more, smaller regions you define, the more boundary-crossing 'migrants' you count. They therefore developed the Aggregate Crude Migration Intensity (ACMI), a scale-standardized intensity that corrects for this modifiable areal unit problem, and embedded it in a four-part framework — intensity, impact, pattern, and distance — that separates the overall amount of migration from its net effect, its spatial structure, and its typical range. Grounded in the measurement conventions of the United Nations migration manuals, the index gives demographers a defensible, internationally comparable answer to the deceptively hard question 'how migratory is this population?'