Ireland's population is officially 6.4 million.

The results of a 2011 census carried out in the Republic, and in the North, have been combined for the first time to generate the figure.

Results show 4.6 million people live south of the border, while 1.8 million live in Northern Ireland.

Since 2002 the population in Ireland has grown by 17%, two and a half times the Norther rate of growth of 6.9%.

Senior CSO statistician Deirdre Cullen says "The timing of the censuses, just two weeks apart, on 27 March 2011 in Northern Ireland and 10 April 2011 in Ireland, offers a rare opportunity to present a detailed picture of the populations of both jurisdictions at a single point in time."

In Northern Ireland, 202,000 people, representing 11% of residents, were born outside the jurisdiction; 37,900 were born in Ireland, representing almost 1 in 5 of the total. In the Republic by contrast, the 58,500 people born in Northern Ireland accounted for just 7.6% of the total 766,800 persons born outside Ireland, who in turn represented 17% of the population.

Age profile

The average age in Ireland is 34, the lowest of any EU Member State. Meanwhile, in Northern Ireland, the average age is three years higher at 37, which was also considerably lower than the EU average of 41.

Reflecting the older age structure, persons aged 65 and over made up 15 per cent of Northern Ireland’s population, compared with 12 per cent of that of Ireland.