By Luis Castro, researcher in the Sustainability NEXUS Research Cluster of the IIASA World Population Program.

The refugee crisis going on across Europe has brought the importance of migration analysis into sharp focus. Policymakers need to know the answers to many questions that require realistic and timely answers, such as:

  • What are the demographic impacts of massive immigration in the short, medium, and long term?
  • What are the impacts on a population’s age distribution if the immigrants are migrating as family units, especially if they have a cultural tradition of large numbers of children?
  • What are the impacts if the immigrants are mainly males of labor-force age?
  • Is there a relationship between education level and the propensity to migrate?

For almost 40 years, IIASA has developed analytical tools and system analysis methods to help answer these questions and others. These methods and tools have been used for UN population projections, as well as by many individual countries around the world, but there is still much research to be done on to help us understand the complex dynamics of migration.

Until the end of the last century, migration modeling was given scant attention. A simple explanation for such lack of interest is perhaps the fact that most social, economic, and demographic research was targeted at the national level. Under such circumstances it was generally assumed that populations were “closed” and international migration was not considered. In addition, demographic studies of sub-national areas used the measure of “net migration”—the number of immigrants minus the number of emigrants—even though this simplifies the situation to the point where key information is lost.

In 1977, just after IIASA had completed its first five years of research activity, the institute announced that a key research theme for the future would be human settlements and services. This focused on developing methods for multiregional demography and included analysis and modeling of age specific migration flows was using data from 17 IIASA national member countries as well as Mexico, which was not yet a member. I dedicated five years at IIASA to developing and testing different migration models investigating patterns of age distributions among groups of migrants, see the graph.


This graph shows how the numbers of migrants of different ages vary. Families migrating, for example, cause a peak in numbers at pre-labor force ages.

Demographic studies often view migration as a collection of independent individual movements. Yet it is widely recognized that many migrations undertaken by individuals whose movements are linked to others. For example, children migrating with their parents, wives with their husbands, or grandparents with their grandchildren.

The aim of my early research at IIASA was to identify some of the effects of family dependency on the migration of men and women, and those of different ages. We developed a model that split migration into independent and dependent flows. This work can explain variations in patterns of migration in societies at different stages of development.

The world has drastically changed since the past 25 years or so, and most nations have become more open and dependent on other countries, more regional alliances have appeared. However, international migration will continue to have the utmost priority for policymakers, not only because of the impacts on the receiving countries but also because of the consequences for the countries of origin.

Note: This article gives the views of the author, and not the position of the Nexus blog, nor of the International Institute for Applied Systems Analysis.

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