Population of Ireland peaked at about 4.4m (estimated) in 2009 and is expected to have devlined since (next census is April so we'll have a clearer picture), Northern Ireland is circa 1.6m in the same year expected to reach 1.8 in 2011. Overall, the island's population is circa 6m, still well down on the pre-famine high of the 1830's at 8.5m (estimated).
JAS