The Brits Abroad project focuses on Britons who live overseas and is centred on research into their number and characteristics by the Institute for Public Policy Research (IPPR), a think tank based in London in the UK.

The figures for Britons living abroad are 2006 estimates drawn up by the IPPR to inform a report it is publishing into the phenomenon of "Brits abroad", which includes recommendations for British government policy.

The researchers who calculated the figures developed different methods that draw on different statistical sources, each with incomplete coverage and varying degrees of reliability.

For example, reliable country census data on the number of British-born or British nationals is available only for a small number of countries. Where figures exist, they are likely to be underestimates as they are out of date (national censuses are typically carried out at the beginning of the decade) and there could have been sizeable growth in the British population since.

The only set of data that does cover every country in the world is the number of UK state pensioners who inform the Department for Work and Pensions that they are resident overseas.

The number of passports issued over the past 10 years does cover most countries, but can be both an over- and under-estimate. On the one hand, replacements for lost and stolen passports could be issued overseas to tourists, but on the other hand, British expatriates may renew their passport when they are back in the UK where it is cheaper to do so.

So, in order to calculate the number of Britons living permanently overseas in 2006, the IPPR developed the following methods:

• Where robust official data exists over time (census or annual population surveys), it has been adjusted in line with previous rates of growth or decline. In Spain, France and Portugal where there is evidence of high rates of non-registration or second-home buying, the official numbers of the British population around popular holiday destinations have been further increased
• Where accurate official data does exist but where trends cannot be calculated, an estimate has been calculated using the growth rate in the number of UK state pensioners in that country
• Where official data is absent, inaccurate or out of date and where UK state pensions data is too small or inappropriate, an estimate of the number of British passports issued during the last 10 years has been used
• Where the passports issuing rates are suspected to be anomalous or where absent, local consular estimates have been used instead.

Also estimated were the number of British expatriates who live overseas for part of the year. Selected countries were categorised into four main groups (far-flung settlement countries, Mediterranean retirement countries, other European or work destinations, and far-flung tourist destinations) before the estimates of Britons living permanently overseas were multiplied by factors based on survey data and other evidence.

Every country has a table showing a figure for the numbers of Britons who live there permanently (the "total") and a combined figure for permanent and part-time Britons ("inc. part-time").

On the same table, some countries have a figure for the number of British pensioners and the gender breakdown of the British population there.

A few countries have tables showing the age and/ or employment breakdown of their British populations.

It means the estimated number of British nationals and/or people born in the UK believed to have lived there for a year or longer.

The figure under "inc. part-time" is the total figure combined with the British nationals and/or people born in the UK who are normally resident in the UK but spend a substantial part of a year (more than three months) in one foreign country. Often these people will own or rent property in that country. It does not include people who travel frequently to a number of countries.

The figure for pensioners is the one set of data used in the research that covers every country in the world. It is data collected by the Department for Work and Pensions on the number of UK state pensioners who inform them that they are resident overseas.

They are not necessarily all British nationals but include foreign nationals who have worked and paid tax in the UK.

Where the breakdown of the British population by gender is provided, this data comes from the respective national statistical offices, in other words from census data or annual population surveys, which range in date from 1996 to 2006.

Where the breakdown of the British population by age is provided, this data comes from the respective national statistical offices, in other words from census data or annual population surveys, which range in date from 1999 to 2006. It should be noted that the figures for some countries are based on small sample sizes.

All the age data refers to UK-born, except for Estonia, Portugal, Greece, France and Japan when it refers to UK nationals.

Where employment data is provided, this comes from the respective national statistical offices, in other words from census data or annual population surveys, which range in date from 2000 to 2005.

All the employment data refers to UK-born, except for Estonia and Spain when it refers to UK nationals.

In some cases the number of Britons living in a country has been estimated at below 100. It is felt this is statistically not robust enough to give precisely, so 1-100 has been used to indicate between one and 100 Britons live there.

As is inevitable in a project of this scope, it was often not possible to obtain figures or accurate figures for all the categories in every country. The use of "n/a" in a table indicates where data was not available.

Inactive people are those aged over 16 not in employment but not classified as unemployed, such as students and people who look after their household. It also includes retired people.

Every country lists the number of Britons who live there permanently, the number of Britons who live there permanently plus Britons who live there part-time, and the number of registered British pensioners. All other data depends on whether it was available to the researchers compiling the figures.

To colour code countries in each region of the world, the total number of Britons in the region has been calculated, and then the percentage of the region's Britons in each country.

If a country has 10% or more of Britons in the region living there, it is coloured as having "most Britons". If a country has 1-9.9% of Britons in the region living there, it is coloured as having "some Britons". If a country has 1% or fewer Britons in the region living there, it is coloured as having "fewest Britons".

For a small number of countries, no data was available and they are coloured grey on the map. They are also not included on the full country list.

For a small number of countries, no data was available and they are not included on the full country list. They are also coloured grey on the map.