By Amanda Ferguson and Padraic Halpin
BELFAST (Reuters) -Northern Ireland has more Catholics than Protestants for the first time, census results showed on Thursday, a historic shift that some see as likely to help drive support for the region to split from Britain and join a united Ireland.
The shift comes a century after the Northern Ireland state was established with the aim of maintaining a pro-British, Protestant "unionist" majority as a counterweight to the newly independent, predominantly Catholic, Irish state to the south.
At that time, the population split was roughly two-thirds Protestant to one-third Catholic.
Data from the 2021 census showed 45.7% of respondents identified as Catholic or were brought up Catholic, compared with 43.5% identifying as Protestants. The previous census in 2011 showed Protestants outnumbered Catholics 48% to 45%.
"Today's results are another clear indication that historic change is happening across this island," said Michelle O'Neill, regional leader of Irish nationalists Sinn Fein, which became the largest party in Northern Ireland's devolved parliament for the first time this year, shocking many unionists.
Sinn Fein said the shift was a further reason why planning should begin for a referendum on a united Ireland. The party has increased calls for a poll since Britain's decision to leave the EU in 2016, which 56% of Northern Irish voters opposed.
"There could be a referendum quicker than we think," said Mark Kelly, 50, a taxi driver from a nationalist part of Belfast whose WhatsApp group chats were buzzing with friends talking about the results.
A vote on Irish unification is at the discretion of the British government, and opinion polls have consistently shown a clear majority favour remaining part of the United Kingdom.
UNIONISM IS 'UP AGAINST IT'
Northern Ireland's sectarian divisions can be traced back to the 17th century, when Protestant settlers from Scotland and England were "planted" in the northeastern part of the island to bolster the authority of the English Crown.
Before a 1998 peace deal, more than 3,000 died during three decades of fighting between mainly Catholic Irish nationalist militants seeking a united Ireland they believed would guarantee their rights, mainly Protestant pro-British loyalists and the British Army.
Demographers have long predicted that Catholics, who tend to be younger and have higher birth rates, could become a majority of voters within a generation.
But while Catholics tend to vote for Irish nationalist parties and support a united Ireland, an increase in Catholic population does not automatically increase support for either.
A significant minority of Catholic and Protestant voters support the cross-community Alliance Party, which doubled its number of seats in the May election. Stripping out religious upbringing, the proportion of people with no religion jumped to 17% from 10%.
"I don't really take heed in it," said Jason Yeo, walking on Belfast's Protestant Shankill Road. The 45-year-old, who plays in a pro-British marching band, said he does not think a United Ireland will happen in his lifetime.
Another census question found that 32% of respondents identified solely as British, down from 40% in 2011, with 29% seeing themselves as Irish, up from 25%. A further 20% said they were Northern Irish.
"On all the demographic indicators and indeed political indicators, unionism is up against it and longer term things do not look good for Northern Ireland's place within the UK," said Jon Tonge, Professor of Politics at the University of Liverpool.
(Reporting by Amanda Ferguson, writing by Padraic Halpin and Conor Humphries, editing by Alex Richardson and Raissa Kasolowsky)