The small republic has been dubbed the fastest repopulating small country in the world. In the last four years alone the population swelled by over three hundred thousand, roughly split between immigrants and births. That lifted the total population to 4.2 million.
It could rise to over five million in about a dozen years, and to six million within a generation. With a growing population in Northern Ireland, the island could match its largest population — more than eight million before the devastating 19th-century famine that prompted waves of emigration — by 2032.
No European Union country has a younger population: statistically, the Irish have been barely aging at all, with the median age staying close to 33. The country will remain young for decades, say experts, and escape the "graying" fate of the rest of Europe.
Edgar Morgenroth, a member of a panel of experts who predict Irish population growth, said the famine started a diminishing of the population that lasted to the late 1960s. "It was only in the 1990s that our population stabilized and started to grow, rapidly," he said. The population might reach the 19th-century level, but it will look very different.
The population changes have been uneven geographically. New houses stretch in a wide arc from north Dublin to the west of the city. But the city's core, despite being replenished by an influx of immigrants, has lost residents to the suburbs and to once unimaginably distant commuting centers in the midlands. In the south, the city of Cork shrank while the county grew.
Some experts think the scale is beyond most citizens' imaginations: in about half a generation, the population may grow by another Dublin, which has 1.1 million people in its greater metropolitan area.
"The worst is that we find ourselves without growing our services to cope with the numbers," Morgenroth said. "The benign outlook is that we have tackled our services and, like Switzerland or Luxembourg, we have great wealth and a great quality of life. The smaller countries can do it right."
Eunan King, an economist at NCB Stockbrokers in Dublin, has long argued that a rising population — more workers and more consumers — will help sustain Ireland's remarkable economic renaissance of the past dozen years.
The largest increases in immigration since 2002 have been from Poland, Lithuania and Nigeria. The latest census showed 63,276 Poles living permanently in Ireland, up from 2,124 four years earlier. In some small districts in Dublin, Limerick and Cork, the census showed, 52 percent of residents were non-Irish, said Aidan Punch, a senior census statistician.
Ireland permits all residents, not just Irish citizens, to cast ballots in local elections. That has helped immigrants win seats in local councils. The mayor of the midlands town of Portlaoise, Rotimi Adebari, is from Nigeria.
To encourage assimilation, the government recently named a minister for integration, Conor Lenihan. The department was organized, Lenihan said in an interview, to show Ireland's commitment to share and develop its new wealth with new arrivals. "We have chosen a midpoint between the U.S. and Europe in terms of our economic success," he said. "I think we can choose a midpoint in integration as well."
Lenihan said his department would investigate ways to provide extensive language classes for adult immigrants and to increase training for unskilled local Irish workers.
But immigrants' representatives say the government needs to do more.
"Ireland should be taking a lead in Europe," said Jean-Pierre Eyanga Ekumeloko, a naturalized Irish citizen from Congo and a co-founder of Integrating Ireland, an independent support group for immigrants.
Ekumeloko said the Irish prime minister should lay out a plan for welcoming and integrating immigrants. He said many were working jobs for which they were overqualified. "A lot of things have changed in interactions between the Irish community and immigrants," he said, adding that in the past he had heard racist remarks. "Things have changed very positively. Now Irish people know Africans."
At a restaurant table in Lucan, in western Dublin, Dulce Huerta, a Mexican, and her husband, an Irishman named Lorcan Donnellan, cradled their 5-week-old child. They talked about the strains population growth was causing in their area, near the district of Lucan Esker, which according to the census numbers is the youngest spot in the country. More children under 4 live there than anywhere else in Ireland.
"The maternity hospital was packed and needed more staff," Huerta said.
They fretted about how the huge housing estates under construction would add to local traffic. "The roads cannot cope already," Donnellan said. "It's going to get more choked."
A new mother at a nearby table, Suzanne Leyden, an actuary, said the authorities seemed to have anticipated the growing needs by opening or expanding primary schools. "Secondary schools will be the next big challenge," she said.
Derek Keating, a local councilor for the Lucan area, said: "The big picture is that we are playing catch-up all the time. There is a lack of infrastructure, in everything from schools to recreational activities."
In the northern Dublin suburb of Swords, Gerard Kelly, a teacher for 25 years and now a principal, said his school would struggle to meet the demand for classroom seats when it opened in September. "Back in 2001 we had 21 children," Kelly said. "Next September we will have 340. We have children from 40 countries."