The traditional Irish family is on the decline, with fewer than one in five Dublin households consisting of a husband, wife and children, figures from the Central Statistics Office (CSO) show.
The statistics also show that men are twice as likely as women to be still living with their parents when they are in their 30s.
The figures, compiled from last year's census, show that the traditional family unit has declined in all the State's main cities since 2002.
Dublin has the lowest proportion of traditional families at 19.4 per cent, followed by Galway at 21.5 per cent, Limerick at 22.2 per cent, Cork at 24.2 per cent and Waterford at 25.3 per cent.
All of the cities had much lower levels of married couples with children than the national average of 32.5 per cent. The highest proportion of traditional families was to be found in Meath, which had 39.5 per cent of traditional family households, followed by Kildare at 38.3 per cent.
Unmarried cohabiting couples are the fastest growing type of family unit in the State. In 2002, the total number of cohabiting couples was 77,600. By last year, this had risen to 121,000, an increase from 8.4 per cent of all family units in 2002 to 11.6 per cent of family units in 2006. Almost two-thirds of cohabiting couples did not have children, according to the census.
Despite the difficulties of getting onto the property ladder, the census figures showed that the number of adult children living with their parents has fallen since the 2002 census. In 2002, there were 304,353 people in their 20s living with their parents, in 2006 that figure had fallen to 208,065.
The number of people in their 30s who are still living at home with their parents has also shown a decline, down from 70,707 in 2002 to 65,963 in 2006.
However, men living with their parents far outnumber women, with men accounting for two-thirds of people in their 30s still at home.
The average household size is continuing to decline and currently stands at 2.8 people per household, compared with 2.94 in 2002. The smallest households are found in cities, with the average household in Dublin having just 2.5 members.
While the population grew by 8.2 per cent from 2002 to 2006, the number of private households increased by a far greater level, from 1.288 million to 1.469 million, an increase of more than 14 per cent, reflecting the trend towards smaller household units.
The traditional family is still the most common type of household, with 477,705 families living in the State. One-person households are the next most prevalent, accounting for 329,450 households. Married couples with no children still outweigh cohabiting couples with no children, with 204,487 married couples as opposed to 65,055 cohabiting couples.
Lone parents accounted for 152,542 Irish households, but the number of lone mothers far outweighed the number of lone fathers, with 130,853 women heading lone-parent households as opposed to 21,689 men.
