This Commons Library briefing paper is a guide to understanding UK migration statistics, explaining the concepts and methods used in measuring migration and setting out a range of data on migration in the UK and in European Union countries.Jump to full report >>
The most comprehensive estimates of long-term migration to and from the UK come from the ONS long-term international migration (LTIM) series, which provides the headline estimates of immigration, emigration and net migration.
A long-term international migrant is someone who changes their contry of usual residence for a period of at least one year. This definition is the international standard used in estimating migration flows in different countries.
Chart 1 in the PDF shows LTIM estimates of immigration, emigration and net migration in the UK from 1991 to 2015. During this period immigration increased 91%, rising from 329,000 in 1991 to 631,000 in 2015.
Emigration increased between 1991 and 2008, but subsequently fell to around 299,000 in 2015, compared with 285,000 in 1991.
Immigration has grown faster than emigration, leading to an increase in net migration from an annual average of 37,000 in the period 1991-95 to an annual average of 249,000 in the period 2011-15.
In the year ending June 2016, work was the most common main reason for immigration, while formal study was the second most common main reason.
Study was the most common main reason for immigration during the period 2009-12, and the reduction in the number of people migrating to the UK to study since then reflects a reduction in the number of Tier 4 student visas issued to students from outside the EEA and Switzerland (see Chart 9 in the PDF).
There are fewer foreign nationals living in the UK than there are people born in other countries. Between January 2015 and December 2015 there were approximately 5.6 million people with non-British nationality living in the UK and 8.6 million people who were born abroad.
The UK’s migrant population is concentrated in London. Around 37% of people living in the UK who were born abroad live in the capital city. Similarly, around 37% of people living in London were born outside the UK, compared with 13% for the UK as a whole.
After London, the English regions with the highest proportions of their population born abroad were the South East (12.4%), the West Midlands (12.1%), and the East of England (12.0%). In each of these regions the proportion of people born abroad was lower than for England as a whole (14.6%), where the percentage was pulled up by London.
Of all the nations and regions of the UK, the North East had the lowest proportion of its population born abroad (5.5%), followed by Wales (5.6%), Northern Ireland (7.0%), and Scotland (7.4%).
There is no single source of data that provides perfectly comparable and up-to-date figures on the number of migrants living in each EU country by either country of birth or nationality. However, by examining statistics from a range of sources, taking account of exactly what they measure, it is possible to make some broad comparisons.
The available data suggests there are roughly around 1.2 million British migrants living in other EU countries, compared with around 3.2 million EU migrants living in the UK.
A migrant can be broadly defined as a person who changes their country of usual residence. Conventionally, there are three different ways of making this definition more precise.
A migrant can be:
Each of these definitions has its strengths and weaknesses. In practice, each of these definitions is used in certain circumstances, depending on the data in question.
This definition is consistent and objective, but it classifies as migrants people who were born abroad but who are nevertheless nationals of the country in which they live (e.g. children born to armed forces personnel stationed in foreign countries).
This definition excludes nationals born abroad, but it also excludes people who have recently changed their country of residence and acquired the nationality of their new home country.
There is also the possibility that when a person is asked their nationality, their self-reported answer may express a sense of cultural affiliation rather than their actual legal status; a problem that does not arise when asking someone their country of birth.
This definition is objective but it poses problems of measurement. People’s intentions regarding their length of stay in a country are subject to change: those people who intend to stay longer than a year may leave more quickly, while those who initially intend a short stay may become permanent residents.
This definition is also somewhat arbitrary; as the number of people meeting it would change were the minimum period of residence longer or shorter than a year.
In migration statistics, stocks refer to the number of migrants usually resident in a country during a particular period, while flows refer to the number of people changing their country of usual residence during a particular period.
Immigration and emigration are therefore flow measurements, recording the number of people entering and leaving the country on a long-term basis.
Statistics on stocks and flows are based on different definitions of a migrant.
Stocks are normally measured as the number of people whose country of birth or nationality is different from that of the country in which they live (the first two definitions above).
Flows are normally measured as the number of people changing their country of residence for at least a year (the third definition).
In the UK, data on stocks and flows comes from different sources. Stocks are measured through surveys of the resident population, while flows are measured primarily though surveys of passengers arriving and leaving the country.
Net migration is the difference between immigration and emigration: the number of people moving to live in a particular country minus the number of people moving out of that country to live elsewhere.
If more people are arriving than leaving, net migration is a positive number, which means net immigration. If more people are leaving than arriving, net migration is a negative number, which means net emigration.
A migrant is someone who changes their country of usual residence. An asylum seeker is someone who does so “from fear of persecution for reasons of race, religion, social group, or political opinion”. In this sense, asylum seekers are generally counted as a subset of migrants and are included in official estimates of migrant stocks and flows.