The UK’s population has hit its highest ever level on record and is projected to grow to 73 million by 2041, mainly thanks to immigration, new data has revealed.

The new figures, published Thursday by the Office for National Statistics (ONS), show the UK’s population in mid-2017 was bigger than ever at an estimated 66 million people and is projected add another seven million over the next 23 years.

The UK’s population will grow by an average of more than 300,000 a year, the equivalent to adding a city the size of Newcastle upon Tyne or Brighton and Hove every twelve months.

In 2017, the population boomed by 430,000 thanks to immigration and births – a grown of 0.6 percent on the year before and adding a city roughly the size of Sheffield or Bristol to the UK.

Over the last 20 years, the ONS said, the main source of population growth in the UK has been migration, with 631,000 people moved to the UK while 349,000 residents moved abroad in 2017 alone.

Today’s publication shows how the UK population in mid-2017 was bigger than ever at an estimated 66m people. It is projected to reach 73m by 2041. Find out more https://t.co/ZuZ76yduKt pic.twitter.com/rzFEyH6gj0 — ONS (@ONS) November 1, 2018

An ever smaller proportion of people in the country are British and fewer were born here, the data also shows.

About 86 percent of the population UK-born and about 90 percent were British nationals in 2017 compared to about 89 percent and 93 percent respectively in 2007.

And in the same 10-year period, between 2007 and 2017, the number of European Union (EU) nationals living in Britain more than doubled from 1.6 million to 3.8 million.

Over the last 20 years, the main source of population growth in the UK has been migration. In 2017, 631,000 people moved to the UK while 349,000 residents moved abroad https://t.co/ZuZ76yduKt pic.twitter.com/snGBDYEhzM — ONS (@ONS) November 1, 2018

Sarah Coates, ONS Statistician for the Centre for Ageing and Demography, commented:

“The UK population has doubled over the last 140 years, reaching a new high of 66 million people in 2017. We project there to be almost 73 million people in the UK by 2041.

“This growth is due to there being more births than deaths and more people moving to the UK than leaving.

“As well as growing, the population is also ageing. From looking at past patterns, we project that more than a quarter of UK residents will be aged 65 years or over within the next 50 years.”