Migration figures: High levels of inward migration into Ireland mean that 10 per cent of the population - or 400,000 people - consists of foreign nationals, census figures indicate.
Ireland now has a proportion of foreign nationals similar to that of countries with a much longer history of immigration, such as the UK or US. A breakdown of the nationality of foreign nationals will not be published until next year.
The number of foreign nationals has risen from 222,000, or 6.8 per cent, recorded during the 2002 census.
Such inward migration was the dominant factor behind the overall population increase from 3.9 million in 2002 to 4.2 million in 2006.
On average there were 46,000 more immigrants than emigrants per year between 2002 and 2006, compared to a corresponding figure of 25,000 between 1996 and 2002.
The numbers arriving here have exceeded those leaving the country since the 1991 census, making it the most sustained period of inward migration in Ireland's history.
Even without inward migration, the population also has been rising as a result of an increase in births and a decrease in deaths. This natural increase rose by an annual average of 33,000 a year between 2002 and 2006, compared to 23,000 between 1996 and 2002.
CSO officials say the figures suggest that the increase in birth rate is due mainly to an increase in the number of women of child-bearing age in the population. There is no indication yet to suggest that the increase is linked to higher numbers of foreign nationals living here.
The highest ever natural increase since the foundation of the State was 40,000 between 1979 and 1982, before entering into a period of decline for the next 15 years.
The population is increasing at the fastest rate since records for the State began in the 1920s. It rose by 2 per cent during the 2002-2006 census period, compared to 1.3 per cent during the previous census period. The previous high for population growth was 1.5 per cent, which occurred between 1971 and 1979.
A more detailed breakdown of the figures shows that all counties in the State have experienced a natural increase in population since the last census. Rates were highest in counties and local authority areas with the youngest age profiles (Fingal, Dublin South, Kildare and Meath) and lowest in counties with the oldest age profiles (Leitrim, Roscommon and Mayo).
A small number of local authority areas recorded net outward migration, including the cities of Limerick, Cork, Waterford, Dublin city, Dublin South and Dún Laoghaire/Rathdown.
A range of factors were linked to the decrease, such as adult children leaving the family home and regeneration projects involving the demolition of older buildings. However, many outlying districts surrounding these areas generally recorded increases, such as suburbs in Dublin, Cork, Limerick and Waterford.