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Multilingual Demographic Dictionary, second unified edition, English volume

Index of migration differentials

Multilingual Demographic Dictionary, second unified edition, English vol.
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Index of migration differentials  (INDEX of migration differentials)

Proportions of migrants 1 can be obtained by relating the number of migrants during a period to the population to which or from which they are migrating. When the proportion of out-migrants 2 is obtained by dividing the number who reported moving out of the area by the population residing in the area at the beginning of the period and alive at the end, this index measures the probability of moving for the population at risk, and among other uses, it can be used in the preparation of population projections where migration is accounted for separately. But other populations are often used in practice as denominators to compute proportions of migrants. Similarly, the proportion of in-migrants 3 is sometimes obtained by dividing the number of in-migrants in an area during a period, by the population of the area at the end of the period; but the denominator could also be the population at the beginning of the period, or the average of the beginning and end populations. The proportion of lifetime in-migrants 4 can be derived from information on the place of birth, dividing the number of persons born out of the area by the enumerated population of the area. The proportion of lifetime out-migrants 5 can be obtained by dividing the number of persons in a country living outside of their area of origin, either by the total number of persons born in that area, or by those among them who still live there. When such characteristics of the migrants as age (322-1), occupation (352-2) or level of education (342-1) are known, indices of migration differentials 6 are used to contrast the migrants and the rest of the population of destination. The index is equal to the quantity 1 minus the ratio of the proportion of migrants in the population having the characteristic studied to the proportion of migrants in the whole population. The index of migration differentials is equal to zero when the population with the given characteristic has the same migration behavior as the rest of the population. The term selectivity of migration 7 indicates that the comparison is between the in-migrants and the population from which they were drawn, at the area of origin (801-4). When comparing the characteristics of the in-migrants to those of the population at the place of arrival (801-5) the term migration difference 8★ is sometimes used.

  • 7. For example, the selectivity of migration from Mexico was decreasing because differences in characteristics between migrants and nonmigrants fade over time; also the origins of Mexican immigrants was increasingly diverse because of the spread of Mexican migration networks in the USA.