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Learning objectives
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Summary
While there is no internationally agreed upon legal definition of international migration, the United Nations Expert Group on Migration Statistics has developed a statistical definition to ensure that countries are measuring the same phenomenon. From a statistical perspective, international migration is broadly defined as a change in residence from one country to another and consists of a spatial (moving from one place to another) and a temporal (for a specified time-period) dimension (Tsegay, 2023). While other characteristics such as the nature (e.g., forced or voluntary or regular versus irregular) or the reason (e.g., family formation or employment) for migration are equally important, they are not crucial to the statistical definition of international migration: a person who changed their place of residence from one country to another is considered an international migrant, regardless of the nature or the reason.
Definitions of an international migrant tend to vary across countries, organizations and studies, which undermines the comparability of migration data. The 1998 United Nations Recommendations on Statistics of International Migration were revised in 2021, resulting in a) amended criteria for establishing residence, b) recognition of the importance of collecting data on temporary mobility or ‘movers’ and c) emphasis on both country of citizenship and country of birth for the identification of foreigners (UN Expert Group on Migration Statistics, 2021). Data on all categories of migrants can be recorded as stock or as flow, although the former are usually more available than the latter. Stock refers to persons residing in one place at a particular point in time (see: International migrant stocks data (migrationdataportal.org)) while flows refer to movements from one place to another over a specific period of time, usually one year (see: International migration flows data (migrationdataportal.org)).
There are, however, other types of migrants/migration that are not covered by the statistical definition of international migration but are equally relevant for the production of migration data and statistics. First, migration can take place within as opposed to across international borders and is therefore referred to as internal migration. Second, migration can happen for a shorter period of time than the conventional minimum threshold for establishing residence and is therefore referred to as temporary mobility. Third, migration can mean the return of migrants to their previous country of residence or repeated movements between two or more countries and is therefore referred to as return migration or circular migration, respectively. Although the vast majority of migrants move within the boundaries of their own country and expectations for the contribution of return and circular migrants to the development of their origin country are high, internationally agreed upon legal and statistical definitions for measuring internal, return and circular migration are lacking.
On one hand, migration can be categorized into different types that differ based on the spatial or temporal dimension, namely, international migration (and emigration), temporary mobility, internal migration, return migration and circular migration. On the other hand, migration can be categorized into different types based on the nature or reason for migration, such as labour migration, forced displacement (which is sometimes considered separately from migration), irregular migration and environmental migration. While international standards and guidelines for measuring the latter types of migrants/migration are less prevalent than those measuring international migration, efforts are underway. For example, the Expert Group on Refugees, IDPs and Statelessness Statistics (EGRISS) recently developed recommendations with clear definitions for statistics on Refugees, IDPs and related populations (EGRISS, 2018; 2020).
In summary, while international migration refers to a change in residence from one country to another, there are other types of migrants/migration that are defined based on the spatial or temporal dimension, the nature of migration or the reason for migration. Table 1 provides an overview of all concepts that will be covered in this chapter and in the Essentials of Migration Data (EMD) more generally and their definitions.