Manual VI - Methods of Measuring Internal Migration

In considering the various alternatives for rate or ratio computation, it should be understood that much depends upon the nature of the problem. Different problems may call for different kinds of rates. Available alternatives may result in trivial differences (for example, if the migration interval is short), in which case the population base that is the most convenient is the one to be preferred. But where differences are substantial, especially where the pattern of differences either over time or between population groups is affected, careful consideration should be given both to selecting the type of rate that is most suitable for the problem at hand, and to the interpretations that are made of the rates that are used.