International migration flows

Definition

Migration flows “refer to the number of migrants entering or leaving a given country during a given period of time, usually one calendar year” (UN SD, 2017). However, countries use different concepts, definitions and data collection methodologies to compile statistics on migration flows. Definitions of who counts as an international migrant vary over time in the same country and across countries.

Data sources and measurement

Statistics on migration flows are based on a variety of data sources depending on the country. Countries may calculate migration flows based on information from administrative sources, such as data derived from issuance of temporary or permanent residence permits and population registries, or they may use sample survey data. The UN Department of Economic and Social Affairs (UN DESA) has compiled data on the flows of international migrants to and from selected countries since 2005. The latest Revision, in 2015, contained data from 45 countries that collected this information (only 43 on emigration flows) – a steady increase compared to 15 countries in 2005, and 29 countries in 2008. However, this has not since been repeated or updated. 

Some countries report data to OECD or the Statistical Office of the European Union (Eurostat) as well. OECD data on permanent migration inflows allow to distinguish between different types of migration flows including work, family and humanitarian migration (OECD, 2023). However, the number of countries reporting flow data is limited and the data are often not harmonized. In addition, UN Statistics Division (UN SD), who has a mandate to collect migration statistics including on migration flows, provides statistics on international travel and migration through their Demographic Yearbook. These migration flows are disaggregated by reason for admission, purpose of staying or going abroad, age and sex. 

Eurostat also provides flows data disaggregated by age and sex, covering the EU-27, Iceland, Liechtenstein, Norway and Switzerland. Frontex’s interactive Migratory Map presents up-to-date on the six main migratory routes into the EU, including numbers of illegal border crossings and top countries of origin per route.

The World Bank Databank presents data on Global Bilateral Migration flows from 1960-2000, disaggregated by country of origin, country of destination, gender and year. Researchers have also developed their own estimates of (bilateral) global migration flows based on 5-year intervals (see  Abel and Cohen, 2019; Raymer et al., 2013). These estimates are based on UN and World Bank statistics on changes in migrant stocks over time.

The International Organization for Migration’s Displacement Tracking Matrix (DTM), a system to track and monitoring population displacement and mobility, collects migration flows data through flow monitoring component in more than 30 countries. DTM flow monitoring assesses areas of high mobility, often at key entry, exit and transit locations. Flow monitoring activities aim to derive quantitative estimates of the flow of individuals through specific locations and to collect information about the profiles, intentions and needs of the people moving. Tools used under this component include baseline assessments at national and local levels, flow monitoring registries and in-depth surveys. 

Data strengths and limitations

The quantification of migration flows is fundamental for the analysis of contemporary migration patterns, particularly the impacts of different factors and policies in countries of origin and destination. Inflow statistics compiled by OECD are available by category of entry, such as whether people moved for reasons of work (including seasonal workers), family reunification, humanitarian protection or others. Numbers of people moving within areas of free circulation such as the European Union or the Southern Common Market (Mercosur) are also indicated separately in the OECD’s International Migration Database.

However, the availability of international migration flows data are limited:

• Flow data from UN DESA are only compiled for 45 countries worldwide or estimated by region, but have not been updated since 2015 (UN DESA, 2015).
• Those countries that do report flows often use different concepts, definitions and data collection methodologies which can make the comparison of flows across countries difficult.
• Flow monitoring tracks movement of people in and out of a country, but is limited in recording international migration, distinguishing one-way and circular migration, and using a systematic sampling frame.  
• There are challenges associated with the use of administrative sources to derive statistics on international migration flows: such sources usually record events (e.g. issuance/renewal/withdrawal of a residence permit) and may not necessarily reflect actual migration movements (e.g. a residence permit is not renewed but the person stays in the country, or the permit is renewed but the person leaves the country).