8.8 Measuring migration

Migration is measured using the same kind of statistics as are applied to other population changes. The crude gross migration rate is the number of people who have moved per one thousand in the mean population. Again, the same applies to the interpretation of this rate as to other crude rates: the mean population includes large numbers who are not exposed to the risk of migration.

It might therefore be useful to calculate the gross migration rate by focusing on the population exposed to the risk of migration. For example, the number of persons who have moved in the age bracket 20-34 could be counted as a proportion of one thousand same-aged persons in the mean population.

To get a more accurate picture of migration it is possible to calculate age-specific migration rates separately for men and women. These rates are usually counted for five-year or one-year age groups. However age-specific migration rates are often computed for the whole population and without gender differentiation. Women do move more often than men, though, so from this point of view it is useful to count the statistics separately for men and women.

The above statistics can be produced separately for internal and international migration. It is also possible to produce separate calculations for out-migration and in-migration. Furthermore, figures for net migration can be calculated using the above methods.