New figures suggest almost half of the foreign nationals assigned social security numbers five years ago are still in the country now.
A Central Statistics Office report revealed that 48% of those who were given PPS numbers in 2004 were still registered for employment or welfare assistance in Ireland by 2008.
The figures are a clear indication of Ireland's recent economic decline.
At the height of the boom in 2006, more than 203,000 PPS numbers were issued to foreign nationals who mostly came from the new EU accession states like Poland and Lithuania.
That fell off in 2007 but dropped dramatically by a third last year.
The CSO data shows that the employment rate for foreign nationals is fairly high in the year of arrival, but then declines rapidly.
That is because many move on, but the study also shows one in four migrants from accession states in 2004 wound up on social welfare last year.
The proportion of foreign nationals claiming social welfare has risen, however.
Of the 118,000 people arriving in Ireland in 2004, 10% registered for benefits but that figure jumped to almost a quarter last year.