Age patterns of migration (cont.)

Direct and indirect effects

Migration has a direct effect on the growth rate of a population by adding or taking away migrants but also has re-enforcing indirect effects.

Indirect effects are caused by differences in the age structure of migrants. If a region has a large proportion of female migrants of child bearing age, the youngest age groups would be relatively large; conversely, if there is a low proportion of females of those ages, the youngest groups would be relatively small.

Exercise

Interaction Complete the sentence about São Paulo state below:

As most migrants are young adults and they usually have lower death rates, and higher birth rates that the general population, so a population with a large number of inmigrants will have crude rate of natural increase (CRNI). On the contrary, a population with a large number of out-migrants will have crude rate of natural increase.

Correct!
No, incorrect.
Incorrect, sorry.
Correct, well done!

 

Hence indirect effects of migration change natural increase in the same direction as the migratory increase.

The effect on the CRNI may be exaggerated even further (or ameliorated) if the migrants have different fertility levels from the rest of the population.

Interaction Why do you think this might be?

Feedback

 

If inmigrants have higher fertility than the native population, and they continue to experience the higher fertility levels after inmigration, then the CRNI in the population will be even higher than would be caused just by an excess of young adults. Conversely, if those who emigrate have higher fertility than the population that is left behind, then there will be a sharper decline in CRNI than would be the case if the adults who left had the same fertility as those who remained behind.