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	Internal Migration Intensity Index	Net Migration Rate
Ämnesområde	Migration Studies	Demografi
Familj	Process / pipeline	Process / pipeline
Ursprungsår	2002	1976
Upphovsperson	Martin Bell and colleagues (IMAGE programme)	Classical vital-statistics measure (formalized by Shryock & Siegel)
Typ	Descriptive index of overall internal-migration propensity	Rate of net population change due to migration per unit population
Ursprungskälla	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.	Preston, S. H., Heuveline, P., & Guillot, M. (2001). Demography: Measuring and Modeling Population Processes. Blackwell. ISBN: 9781557864512
Alias	Crude Migration Intensity, Aggregate Crude Migration Intensity, CMI / ACMI, Migration Intensity Measure	Net Migration Ratio, Crude Net Migration Rate, Net Migration per 1000
Närliggande	3	4
Sammanfattning	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?'	The net migration rate expresses the net effect of migration on a population's size as a rate: net migration — in-migrants minus out-migrants over a period — divided by the population at risk, conventionally stated per 1000 people. It is the migration counterpart to the rate of natural increase and a standard component of population accounting. Because directional migration flows are often poorly recorded, net migration is frequently not counted directly but estimated as a residual from the demographic balancing equation or by comparing surviving cohorts across two censuses.