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Migration Data: Our sources and definitions

In our Migration Data Explorer we present a range of metrics on migration, refugees, asylum seekers, internal displacement and remittances.

This data comes from a combination of international sources. Below we provide details on the original source and its definitions. When citing this work, please also cite the original data sources.

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Immigrant and emigrant stocks

Where do we source data on immigrant and emigrant stocks from?

Data on immigrant and emigrant stocks is sourced from the United Nations Department of Economic and Social Affairs (UN DESA).

What is the difference between an immigrant and an emigrant?

Migrants have both an origin and a destination, meaning that international migrants can be viewed from two directions:

  • Emigrant: someone leaving their country of birth (origin)
  • Immigrant: someone moving to a country that they were not born in (destination)

How does the UN define a migrant?

Based on the data source –  the United Nations Population Division – an international migrant is someone who has been living for one year or longer in a country other than the one in which he or she was born.

This means that many foreign workers and international students are counted as migrants. Additionally, the UN considers refugees and, in some cases, their descendants (such as Palestinians born in refugee camps outside of the Palestinian territories) to be international migrants.

Estimates of the number of unauthorized immigrants living in various countries are also included in the total counts.

Tourists, foreign-aid workers, temporary workers employed abroad for less than a year and overseas military personnel typically are not counted as migrants.

Where does the UN sources its estimates from?

The UN provides estimates of global migration using a combination of population census; demographic data; and, where data is not available, modeled estimates.

For the majority of countries, the UN defines immigrants or emigrants on the basis of country of birth. This means an immigrant is defined as someone who was born in a country that is different from their current country of residence. This is the case, even if they acquire citizenship in the country that they have moved to.

However, the UN also notes that for some countries data on the place of birth is not available. In these cases, the country of citizenship is used as the basis of migrant status.

Does the UN measure migrant stocks or flows?

Data on migration from the UN measures the stock of migrants in a given country, which is the total number at any given time. This does not measure the flow of migrants.


Net migration

Where do we source data on net migration from?

Data on net migration is sourced from the United Nations Department of Economic and Social Affairs (UN DESA).

What is net migration?

Net migration is the total the number of immigrants (people moving into a given country) minus the number of emigrants (people moving out of the country).

This is measured over the previous five years and is expressed as the average annual net number of migrants.

What is net migration rate?

Net migration rate is the number of immigrants (people moving into a given country) minus the number of emigrants (people moving out of the country) in the previous five years, divided by the person-years lived by the population of the receiving country over that period.

It is expressed as the average annual net number of migrants per 1,000 population.


Child migrants

Where do we source data on child migrants from?

We provide two metrics on child migrants: one on the number of children under 15 years old; and one with the number under 18 years old.

Data on child migrants under 15 years old is sourced from the United Nations Department of Economic and Social Affairs (UN DESA).

Data on child migrants under 18 years old is sourced from UNICEF.

How does the UN define a child migrant?

The UN defines a child migrant as any person under 15 or 18 years old (based on the two age thresholds that we present) that meets the overall criteria for an international immigrant or emigrant.

That is, anyone who has been living for one year or longer in a country other than the one in which he or she was born.

Child migrants are measured as the stock of migrants in a given country, which is the total number at any given time. This does not measure the flow of migrants.


Asylum seekers

Where do we source data on asylum seekers from?

Data on asylum seekers is sourced from the United Nations High Commissioner for Refugees (UNHCR).

How does the UNHCR define asylum seekers?

“Asylum” is a term that is not defined in international law, but has become a universally-recognized term for the protection provided by a country to refugees and other persons in need of international protection on its territory.

The need for international protection arises when a person is outside their home country and unable to return home because they would be at risk there, and their country is unable or unwilling to protect them.

Risks that give rise to a need for international protection classically include those of persecution, threats to life, freedom or physical integrity arising from armed conflict, serious public disorder, or different situations of violence.

Other risks may stem from: famine linked to situations of armed conflict; or disasters; as well as being stateless.

“Asylum seeker” is therefore an individual that has an application for asylum pending at any stage in the approval process in a country that is different from their home country.


Refugees

Where do we source data on refugees from?

Data on refugees is sourced from the United Nations High Commissioner for Refugees (UNHCR).

What defintion does the UNHCR use for refugees?

Refugees are, by definition: in need of international protection, being outside their country of origin because of serious threats against which the authorities of their home country cannot or will not protect them.

In addition, individuals who are outside their country of origin (typically because they have been forcibly displaced across international borders) but who may not qualify as refugees under international or regional law, may in certain circumstances also require international protection, on a temporary or longer-term basis.

This may include, for example, persons who are displaced across an international border in the context of disasters or the adverse effects of climate change but who are not refugees. In such situations, a need for international protection would reflect the inability of the country of origin to protect against serious harm.

Who are resettled refugees?

Resettlement is the change in status of a refugee when they go from an asylum country/state to another territory that has agreed to admit them and ultimately grant them permanent residence.


Internal displacement

Where do we source data on internal displacment from?

Data on internal displacement is sourced from the Internal Displacement Monitoring Centre (IDMC).

How does the IDMC define internal displacement?

Internal displacement refers to the forced movement of people within the country they live in. IDMC adopts the definition of an internally displaced person (IDP) categorized in the Guiding Principles on Internal Displacement:

Internally displaced persons are persons or groups of persons who have been forced or obliged to flee or to leave their homes or places of habitual residence, in particular as a result of or in order to avoid the effects of armed conflict, situations of generalized violence, violations of human rights or natural or human-made disasters, and who have not crossed an internationally recognized State border.

IDMCC focuses on three criteria to define a displacement event:

  • Forced nature of displacement: someoone that is internally displaced is differentiated from a migrant on the basis of their displacement being forced.
  • Displacement from their habitual residence: forced displacement is not always associated with a fixed place of residence. For example, for nomadic pastoralists, displacement may be the result of the loss of traditional grazing areas, the death of livestock, or a both. Given that the concept of habitual residence is intimately linked to peoples’ livelihoods, some people who have lost their livelihoods can be considered as internally displaced. An example of this is pastoralists who have become displaced due to the impacts of drought and conflict.
  • Must be displaced within their country of origin or habitual residence – Internally displaced persons are only classified as such while they remain within national borders. Once they cross a border, they are then classified as an international migrant, or refugee.

What metrics does the IDMC use to define internal displacement?

The IDMC uses several metrics to measure internal displacement. In our Migration Data Explorer we present two: new displacements, and the total stock of displacements.

New displacements: this is the number of new displacements that occur within a given period of time (in the case of the data we present, one year). It is a flow measure since it records the number of new events. This indicator measures events rather than individuals. The same person could be displaced several times, and each time counts as a new displacement.

Total cumulative displacements: this is the number of displacements that are still ongoing at a given time. It is a cumulative stock measure. It is calculated as the sum of new displacements over time minus returns flows of internal displacements. When someone returns to their home, crosses the border into another territory, dies, or settles elsewhere, then they are subtracted from this cumulative stock.


Remittances

Where do we source data on remittances from?

Data on remittances is sourced from the World Bank based on underlying data from the International Monetary Fund (IMF); World Bank and OECD.

What are remittances?

The source defines remittances as:

Personal remittances comprise personal transfers and compensation of employees. Personal transfers consist of all current transfers in cash or in kind made or received by resident households to or from nonresident households. Personal transfers thus include all current transfers between resident and nonresident individuals.

What employees are included?

The source defines ‘compensation of employees’ as the income of border, season and other short-term workers who are employed in an economy where they are not resident.

What are remittance costs?

Remittance costs are explained by the International Monetary Fund (IMF) as:

The costs of a remittance transaction include a fee charged by the sending agent, typically paid by the sender, and a currency-conversion fee for delivery of local currency to the beneficiary in another country.

Some smaller operators charge the beneficiary a fee to collect remittances, presumably to account for unexpected exchange-rate movements.

And remittance agents (especially banks) may earn an indirect fee in the form of interest (or “float”) by investing funds before delivering them to the beneficiary. The float can be significant in countries where overnight interest rates are high.


Population adjustments

For a range of metrics we calculate our own population-adjusted values.

To do so we divide the original metric (for example, number of emigrants) by a country’s total population.

The population data used in this calculation is our Our World in Data population series which relies on the UN World Population Prospects for the years covered in this migration dataset. We describe how this population dataset is constructed here.

Annual data adjustments

Some metrics, which are reported annually, come with high levels of volatility which limits their usability.

However, volatility and sudden changes are important signals for understanding migration due to conflict or disaster. To make these changes more understandable, while maintaining the important signals of year-to-year changes, we have re-calculated annual data as the rolling five-year average.

This is the case for metrics that we present on refugees, asylum seekers, resettlement, internal displacement and remittances.

Explore in our Migration Data Explorers