If Britain's official estimate of the scale of recent migration could be out by a few hundred thousand people, what about Ireland's?
The Minister of State for integration, Conor Lenihan, said recently he believed last year's census gave a "serious underestimate" of the number of foreign nationals living in the country and speculated that the non-Irish population could amount to 13-15 per cent of the total, rather than the 10 per cent reported in the census.
But the census is by far the most rigorous and comprehensive study to be carried out, and there is no hard evidence to contradict its findings. In its defence, the Central Statistics Office (CSO) can point to a census campaign that lasted 20 weeks, during which all 1.8 million households in the State were visited - many several times - by more than 5,000 enumerators.
It's possible that the CSO missed people, but if the totals are wrong to the degree that is alleged, enumerators would have missed about a quarter of a million people, all of them foreign nationals. And if so many were missed, their presence would almost certainly show up in other indicators, says one expert. If foreign nationals accounted for 15 per cent of the population by April 2006, then the quarterly national household survey, for instance, would be showing labour force growth to be more than double the 4.5 per cent it was indicating for a number of years up to census day.
But there are serious problems with the State's statistics, nonetheless. As the Immigrant Council has pointed out, data collected by government departments are not always compatible and are rarely collated. It suggests that such information - crucial for planning on schools, infrastructure and integration - should be collated and published by one source.