One in 10 highly-skilled Britons lives overseas, according to a new study, as emigrants enjoy higher pay and better health.
The research by University College London also shows millions of immigrants with low levels of numeracy have entered the UK, although incomers are overall more likely to hold a degree than native Britons.
An estimated 4.7 million British nationals are living abroad, mostly to Australia, the US and Canada, the study said.
In a report, published today, lead researcher Dr John Jerrim of the UCL Institute of Education said "approximately one in 10 highly-skilled British citizens now lives overseas".
Emigrants were earning more money and reported better health than so-called UK "stayers", but were working considerably longer hours.
Britons working in North America and Australia earned 4,000 US dollars per month compared with the equivalent of 3,200 dollars in the UK, although they worked an average of 55 hours compared with 44 for stayers.
And 86% working in North America reported very good or excellent health, compared with around 61% of stayers.
"Little was previously known about the employment, earnings or quality of life of UK emigrants compared to the individuals who remain in this country," Dr Jerrim said.
"Overall, although there are some important differences in regards to career paths and wages, these are perhaps not as pronounced as one might expect. It seems that, although many individuals move in search of a better life abroad, this may not always be achieved."
The analysis of UK emigrants, immigrants and "stayers" suggested 684,000 highly-numerate Britons left the country between 1964 and 2011, to be replaced by an almost equivalent number of immigrants with strong numeracy skills.
But around 2.4 million people with poor number skills had entered the country, accounting for one in four working-age UK innumerate adults.
"Although immigration from south Asia has added many highly numerate people to our labour force, immigration from the same region and Africa has added six times more people with low numeracy skills to the UK than those with high numeracy skills," Dr Jerrim said.
"Immigrants account for one in four of the 9.6 million working age adults living in the United Kingdom with low-level numeracy skills. Immigration has therefore had its biggest impact upon the bottom end of the numeracy skill distribution; it has led to a significant increase in the supply of low-skilled workers."
Dr Jerrim analysed data on 24 countries gathered by the Organisation for Economic Co-operation and Development (OECD). The study focused on 7,628 UK 'stayers', 843 immigrants into the UK and 1,324 emigrants, aged 16-65.
The findings also showed around 37% of immigrants held a bachelor's degree or higher, compared with 21% of stayers.