House of Commons Library

Migration Statistics

Published Friday, February 23, 2018

This Commons Library briefing paper is a guide to understanding UK migration statistics. It explains 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.

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UK migration

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.

The chart below shows LTIM estimates of immigration, emigration, and net migration in the UK from 1991 to 2016. During this period immigration increased 79%, rising from 329,000 in 1991 to 589,000 in 2016.

Long-term international migration in the UK


Long-term international migration in the UK

Emigration increased from 285,000 in 1991 to 340,000 in 2016.

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 256,000 in the period 2012-16.

Why do people migrate to the UK?

In the year ending December 2016, work was the most common main reason for immigration (275,000), while formal study was the second most common main reason (137,000).

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).

Migrants living in the UK

There are fewer foreign nationals living in the UK than there are people born in other countries. Between January 2016 and December 2016 there were approximately 6.0 million people with non-British nationality living in the UK and 9.2 million people who were born abroad.

The UK’s migrant population is concentrated in London. Around 36% of people living in the UK who were born abroad live in the capital city. Similarly, around 38% of people living in London were born outside the UK, compared with 14% for the UK as a whole.

After London, the English regions with the highest proportions of their population born abroad were the West Midlands (13.1%), the South East (13.1%), and the East of England (13.0%). In each of these regions the proportion of people born abroad was lower than for England as a whole (15.4%), 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 (5.8%), followed by Wales (6.0%), Northern Ireland (7.6%), and Scotland (8.6%).

Migration between the UK and other EU countries

The available data suggests that in 2011 there were around 0.9 million British nationals living in other EU countries, while in 2016 there were around 3.6 million EU nationals living in the UK.

Definitions of a migrant

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:

  1. Someone whose country of birth is different to their country of residence.
  2. Someone whose nationality is different to their country of residence.
  3. Someone who changes their country of usual residence for a period of at least a year, so that the country of destination effectively becomes the country of usual residence.

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.

Statistical concepts

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).

Stocks and Flows within UK data

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

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.

The difference between migrants and asylum seekers

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.

Publication details

Commons Briefing papers SN06077

Author: Oliver Hawkins

Topics: Immigration, Population

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