Figures shows we're the most prolific in Europe for making babies
THE population boom has been driven by our birth rate -- the highest in the EU, Census 2011 shows.
Despite large numbers of people leaving the State because of the recession, the surging birth rate means the population has not gone into decline.
Some 363,500 babies were born between 2006 and 2011, while 140,700 people died in the same period.
The difference of 222,800 is called the 'natural change', and Ireland's rate is far higher than our European neighbours.
The Central Statistics Office (CSO) said in 2008, the last year for which figures are available, the Irish rate of natural change was 10.4 per 1,000 population. This compared with an EU average of 1.2pc.
But migration also swelled the population, with 118,650 people coming to live here between 2005 and 2011, an average of 23,730 a year.
This is a sharp decline on the 47,832 who arrived annually in the last census period, but the CSO said final migration figures would not be available until next April, when the data was analysed.
The CSO uses two methods to qualify migration patterns -- the quarterly household survey and the census. Estimates from the CSO in April 2010 suggested that the population was 4.47 million, but the census shows it stands at 4.58 million -- a difference of 110,000.
This is because the census is the only way to accurately measure migration, and it only happens every five years.
"Migration is measured through the quarterly national household survey," CSO assistant director general Padraig Dalton said.
"That identifies people who were in the house the previous April who have left, and those who have returned. We interview about 60,000 to 70,000 people a quarter. You can capture inflows (people who have arrived) quite well, but if the whole household has left, it's difficult to capture.
"In the census you go to every single household. There's only one question -- the one-year inflow -- where people are asked if there's anybody in the house who has arrived in the past year. One of the main reasons we have a five-year Census is because it allows us to get a handle on migration."
Census 2011 shows that the population grew in every county, with growth rates highest in Laois (up 20pc), Cavan (up 13.9pc), Fingal (13.8pc), Longford (13.3pc) and Meath (13pc).
The population fell in Cork and Limerick cities, by 0.4pc and 5pc respectively, but in both cases the population increased in the surrounding counties.
The highest birth rates were in Fingal, South Dublin, Kildare and Meath, and the lowest in Roscommon, Mayo and Cork city.
Despite fears that emigration will rise, the CSO says the population is still expected to increase over the coming years.