Just 3% of the population of Caerphilly County Borough were born outside of the UK, according to latest figures.
Estimates from the Office for National Statistics show that only 3% of the area’s 181,000-strong population across the year to June were born overseas.
This was the same rate as in June 2016, the earliest period with comparable data.
The figures are based on the Annual Population Survey, and are rounded to the nearest thousand.
They count people living at private addresses and students in halls of residences whose parents are based in the UK, but exclude people living in communal buildings such as hostels or hotels.
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Of the 5,000 people living in Caerphilly who were born outside the UK, most (60%) were from the European Union.
A further 20% were from Oceania.
Across the UK, 14% of the population across the year to June was born overseas, the same rate as three years earlier.
But India has knocked Poland off the top spot as the most common non-UK country of birth, the first time since 2015 that the EU nation has not been in first place.
According to Robert McNeil, deputy director of the Migration Observatory at Oxford University, there has been a big fall in EU net migration to the UK, with data suggesting that more migrants from the EU8 countries that joined the EU in 2004 are leaving than arriving.
“Population data seems to support this, as Polish-born people are no longer the biggest foreign-born group in the UK, with India reclaiming that top spot,” he said.
“It’s hard to know exactly why this big drop in EU net migration has happened, but the fall in the value of the pound and less of a sense of security for EU migrants in the UK since the referendum are both likely to play a part.”
He added that the populations of Polish and Indian-born people tend to be concentrated in different areas around the UK, with Indian-born populations often concentrated in more urban areas, and many Polish communities in smaller market towns and more rural areas.
The area with the highest proportion of non-UK born residents was Brent in London – its overseas-born population stood at 54%.