Kamus Demografi Pelbagai Bahasa, Edisi Kedua, Volum Bahasa Malaysia

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812

Migration statistics¹ are compiled to reveal the volume of migration, the direction of migratory movement and the characteristics of migrants. The accuracy with which each of these kinds of facts is ascertained depends upon the method of compilation, as most migration statistics consists of approximations and estimates rather than precise measurements. Direct measurement of migration² requires a system of recording movements as they occur. The most complete migration statistics are developed from population registers in which all changes of residence are recorded. They allow measurement of internal and of international migration, but are more satisfactory for the former than for the latter. In countries where these population registers do not exist, a certain number of administrative record systems which do not cover the entire population can be used for particular purposes. Thus, voter registration records³, social security records⁴ or tax-payers records⁵ may yield information on internal migration. In the case of overseas migration, statistics may be based on passenger lists⁷ or manifests⁷ of ships and aircraft. Counts of persons crossing a political frontier yield only very crude data; most of all in areas with much frontier traffic (803-2*) special steps must be taken to distinguish migrants from travellers⁸, who do not change their place of residence, and persons in transit 801-11). The number of visas⁹ or entry permits⁹ granted and the number of residence permits¹⁰ or labor permits¹¹ issued may also be used as an indication of the migration of foreign nationals.

813

Maklumat yang dikumpulkan melalui banci dan tinjauan membolehkan pembangunan statistik berkenaan migran¹. Bergantung pada soalan-soalan yang ditanya, kebiasaannya ia mengandungi statistik migran masuk², statistik migran keluar² dan statistik tempat kelahiran³. Pendekatan ini mempunyai kekangan untuk kajian migrasi antarabangsa; di mana emigran tidak boleh diketahui sementara imigran adalah diketahui, apa jua negara asal mereka.

814

Where it is not possible to determine migration directly, indirect estimates of net migration may be obtained by the residual method¹ or method of residues¹ in which the change in population between two dates is compared with the change due to natural growth; the difference between the two figures is attributed to migration. The vital statistics method² consists of computing the difference between total population change, as assessed from two censuses, and natural increase (701-7) during the intercensal period. The survival ratio method³ is commonly used to estimate net migration by age; it does not require actual death statistics. Survival ratios may be derived either from life tables or from the comparison of successive censuses, and they are applied to a sub-population in one census to give expected numbers by age at the time of the other census. A comparison between the observed and the expected population may be used to estimate the balance of migration by age for the subpopulation. When Templat:NewTextTerm (813-3) by age and current residence are available in two consecutive censuses, it is possible to make indirect estimates of migration streams.

815

Istilah generik kadar migrasi¹ merujuk kepada sebarang kadar yang mengukur kekerapan relatif migrasi dalam populasi. Melainkan dinyatakan sebaliknya, kadar ini perlu digunakan sebagai kadar migrasi tahunan². Ia boleh diperolehi melalui nisbah antara purata bilangan pergerakanan semasa tahunan sepanjang tempoh tertentu kepada purata penduduk dalam tempoh tersebut. Kadar migrasi berih tahunan³ dan kadar migrasi jumlah tahunan⁴ adalah dikira dengan menggunakan maklumat yang bersesuaian dengan migrasi bersih dan migrasi jumlah. Indeks kekesanan migrasi⁵ atau indeks kekesanan⁵ adalah dikira sebagai nisbah antara migrasi bersih kepada jumlah migrasi dalaman dan migrasi luaran. Julat bagi indeks tersebut adalah daripada sifar, apabila ketibaan dan pelepasan adalah sama, kepada satu apabila migrasi adalah daripada satu hala sahaja.

816

Proportions of migrants¹ 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-migrants² 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-migrants³ 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-migrants⁴ 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-migrants⁵ 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 differentials⁶ 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 migration⁷ 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 Templat:NewTextTerm or Templat:NewTextTerm is sometimes used.

817

Longitudinal migration analysis¹ requires information on the successive moves of an individual over time, information which is normally available only from population registers (213-1) or retrospective surveys (203-8). Several refined measures of migration are available from this type of data, such as a first migration probability², defined as the probability that a group of non-migrants³ aged x will be involved in migration for the first time before reaching age x + n . These probabilities can be used to calculate a non-migrant table⁴. The latter, when combined with a life table (432-3) will lead to a double decrement survivorship schedule of non-migrants⁵. Similarly, migration probabilities by order of move⁶ can be computed, as well as the proportion of migrants of a given order who have not gone on to make a subsequent move within a certain migration defining interval. The all orders migration rate⁷ is the ratio of moves of all orders in a year to the average population size of the cohort (117-2) over the year. The cumulation of these rates for a cohort up to a given date provides an estimate of the mean number of moves⁸ in the absence of mortality. A survivorship schedule can be combined with an age-specific all orders migration table⁹ to estimate the average number of remaining moves for an individual of a given age, given the prevailing mortality.

818

In studying migrants between two areas during a period, one commonly used measure is the index of migration intensity¹, obtained by dividing the number of migrants from area A to area B by the product of the number of inhabitants in B at the end of the period, and the number of inhabitants of A at the beginning of the period who are still alive at the end. This index, divided by the ratio of the total number of migrants to the square of the population of the country, yields a migration preference index². When the numerator is restricted to the net stream of migration, the resulting measure is called an index of net velocity³. The effectiveness of migration streams⁴ is measured by relating the absolute value of the net migration stream to the gross interchange (805-10).

819

Migration models¹ fall in two broad categories. The first relates migration streams (803-9) between two areas to social, economic or demographic variables. These variables are often classified as push factors² when they characterize repulsion² from the area of origin, as pull factors³ resulting in attraction³ to the area of destination, and as intervening obstacles⁴ between the two areas. The simplest of these models are gravity models⁵: the streams between the two areas are directly proportional to the size of their population, and inversely proportional to the distance⁶ between them, raised to a certain power. Other models consider that the streams are proportional to the opportunities in the area of destination, and inversely proportional to intervening opportunities⁷ between origin and destination. Models in the second broad category are stochastic models (730-5) and refer to individuals rather than to populations; they link the probability of migrating to a certain number of personal characteristics such as age or the previous history of migration.