The Big Question: How many Britons live abroad, and why do they leave home?

Why are we asking this now?

Tracking emigrants has become difficult as recent censuses have not tried to calculate the numbers, but the Institute for Public Policy Research (IPPR) yesterday issued a report that is the first attempt to put a figure on the number of Britons who are currently living abroad. Their researchers estimate that there are 5.5 million expat Britons, rising to almost 6 million if that figure is expanded to include those who live or work abroad for part of the year, such as those with second homes or students and employees on foreign secondment. Last year, 198,000 people left the UK to start a new life abroad.

So is all this emigration new?

Britons have always emigrated, but the reasons have changed somewhat over the centuries. Some early émigrés had little choice about the matter, from those who fled persecution in England to make a new life in America in the 17th century, to the convicts who were forcibly transported to Australia in the 18th and 19th centuries. At the same time, tens of thousands of others left Britain more voluntarily to find new fortunes and careers in the countries of the Empire, such as India and Africa.

The 1861 census estimated that 2.5 million people were living abroad, rising to 3.9 million in 1881. Emigration peaked in 1966-67, when 468,000 people left the UK. That included many "Ten Pound Poms" who had been lured to a new life in Australia, in the decades after the Second World War by the offer of cheap passages and the promise of jobs.

Where do they go?

They may no longer be shackled convicts or Ten Pound Poms, but the largest number of Britons to be found abroad is still in Australia. The IPPR report estimates that there are 1.3 million British expats living permanently down under, accounting for 23 per cent of all those living abroad for a year or longer.

Spain is the second most popular destination, with 761,000 expats, rising to 990,000 when second home-owners and other part-time residents are taken into account. The US has more than 600,000 Britons living there, while Canada, Ireland, New Zealand and South Africa are all in the top ten destinations.

Three quarters of all British expats live in the top ten destination countries. But Britons have spread themselves across the globe; 41 foreign nations each have a UK expat population of at least 10,000 and 112 countries have at least 1,000 British people in their midst.

While the big expat populations will come as no surprise, the demographics further down the destination league table are more interesting. An estimated 160 Britons are living permanently in Cuba, including five pensioners. A further 940 have made Iceland their home, while 770 Britons are permanently resident in Kazakhstan, made infamous by the Borat movie.

Patterns of emigration are also changing, with a doubling in the annual number of Britons going to live in Europe over the past decade to more than 70,000 a year. New generations of expats are moving away from the "old Commonwealth" countries to new destinations and buoyant economies in Asia and China.

Why do they go?

As with the destinations, the reasons are disparate. More than a third of those who are currently living abroad say they chose to go for professional and educational opportunities, which is reflected in the fact that half of all emigrants are aged between 25 and 44. A fifth had moved for family and personal reasons, one in four had gone for a better lifestyle and climate, while 11 per cent said they wanted to "have an adventure."

The IPPR survey highlighted that most people live abroad for the positive attributes of their destination, rather than negative opinions of life in the UK. When people who were considering emigrating were questioned, only 12 per cent said they were contemplating a new life abroad because they did not like Britain or what it was becoming.

Statistical analysis by the IPPR also showed that when house prices increase, so does emigration, while a stronger pound is also associated with high rates of movement abroad. Emigration also increases when unemployment is low, according to the research - the more buoyant the economy here, the more confident Britons feel about expanding their horizons. Some go to study abroad - an estimated 14,500 Britons went to study at foreign universities in 2004, some 8,000 of them in the US.

In addition, there are currently 2,351 UK nationals in foreign jails, 35,000 members of the armed forces living overseas and, during 2005, 46 UK nationals who applied for asylum in the US, eight of whom were successful.

Do they come back?

Some certainly do - research has suggested that 25 per cent of the Ten Pound Poms who went to live in Australia in the Fifties and Sixties eventually returned to Britain and it is thought that the rate has remained the same for those who relocate anywhere else nowadays.

According to figures from the Office for National Statistics, 91,000 Britons who had been living abroad came back to the UK in 2005. But many of these may have been students on gap years, workers returning from secondments and other expats who have come to the end of a planned sojourn abroad.

More than half of highly skilled emigrants who returned to the UK did so for professional and educational reasons or because of visa requirements or their children's education. However, there are signs that the rising cost of living in European countries such as Spain may be driving people back to Britain, particularly elderly people who run out of funds and find that some EU countries do not have the same provision of care homes and help as found in the UK. Alongside them are the people who want to come back but cannot afford to because of the high cost of living in Britain.

More than half of expats living abroad said they would not swap their lifestyle and climate for that of Britain. But 14 per cent cited "cost" as a main reason for not returning to the UK - increasing to a quarter of those living permanently in Spain.

Is this emigration damaging Britain?

Since the Sixties, there have been concerns that an increase in the number of Britons going to live abroad could lead to a "brain drain" of academics, skilled manual workers and professionals to foreign countries. Between 1966 and 2005, the UK experienced a net loss of 2.7 million British nationals - meaning that every year for the past 39 years, 67,500 more people left the UK than came back to it. But although Britain has lost an estimated 1.38 million of its own citizens working in professional and managerial occupations to overseas nations in the past 25 years, it has actually gained 1.42 million foreign workers at the same level.

And while much controversy has surrounded the influx of manual workers from new EU countries such as Poland, many thousands of Britons with the same skills are emigrating in the same search for a better life.

Is British life driving people abroad?

Yes...

* High house prices and the cost of living in the UK are cited by many people as a reason for leaving

* The influx of cheap labour from new EU countries has coincided with an increase in the number of manual labourers emigrating

* Universities abroad pay far higher salaries to researchers and teachers than comparable British institutions

No...

* Only 12 per cent of people say they live abroad because they do not like what Britain has become

* Many people go abroad to do a job, but return for 'professional development' - so it can't be that bad here

* Researchers say that 'push' factors are not enough to make people leave - 'pull' factors are far more important