Update 3.45pm: The population could swell to 6.7 million by 2051, according to projections by the Central Statistics Office.
The CSO says with current fertility and projected immigration rate, the population will increase by almost two million.
Chief Economist with Davy Stockbrokers Conal MacCoille has said that will put even more pressure on housing.
He said: "There are very few houses in Dublin.
"I think this sort of highlights we really do need a proper national plan to develop the country beyond Dublin and get the infrastructure in place.
"We had the summer economic statement yesterday planning very large increases in capital expenditure on housing and roads.
"Today's projections show we need to roll that money out and start building on infrastructure."
Earlier: Unemployment fell by almost 20% (18.6%) in the year to March – a fall of 30,000 people.
The Central Statistics Office has published its Labour Force Survey for the first three months of the year.
The number of people in work has increased by 3% (2.9%) – with 2.2 million people now working.
The number of people classed as long-term unemployed, meaning they’re out of work for a year or more - has fallen by 40%.
Jim Dalton, a statistician with the CSO said: "The total number of persons classed as long-term unemployed was 50,100, and that's down by 34,800 or 40.9% for quarter one 2017.
"Long term unemployment has been declining on an annual basis since the fourth quarter of 2012 and in quarter one of 2018, 37.7% of all unemployed persons were so for 12 months or longer."