The data, published in the CSO's Households and Families document, showed that number of separated and divorced people increased by 22.3 per cent between 2006 and 2011, from 166,797 to 203,964.
Two thirds of the increase (24,784) was among those aged 55 and over.
While married people on their first marriage accounted for 48.5 per cent of the adult population in 1996, this has fallen to 45.9 per cent in 2011. However, this figure is a slight increase on the 45.1 per cent recorded in 2006.
The married population increased by 9.2 per cent between 2006 and 2011, growing from 1,565,016 to 1,708,604, a reflection of the fact the population increased overall. Married people as a percentage of the adult population was 49.6 per cent, lower than the equivalent figure in the US.
The percentage of married people over 18 in 1986 was 61 per cent.
There were 88,918 separated and divorced men in 2011 and 115,046 women. The numbers are very similar for men and women up to age 45 after which they begin to diverge as the number of separated and divorced women outstrip their male counterparts.
Between 1996 and 2011, the number of people who were re-married following divorce or annulment increased from 6,641 to 42,960, a rise of 550 per cent. The peak age for divorce among both men and women was 48 with 1,461 and 1,935 persons respectively.
The census has repeatedly shown more divorced women than men in Ireland with varying explanations, one of which is the higher numbers of men who re-marry following divorce.
The figures also showed that there were significant differences between the marital structure of the Irish national population aged 15 and that of the non-Irish population.
The percentage of singles among Irish and non-Irish nationals was broadly similar (41.6 per cent and 42.0 per cent respectively) as was the percentage in their first marriage (46.2 per cent and 44.6 per cent respectively). However, contrasts emerge between the two groups when examining the remaining categories.
Fewer than eight per cent (7.8 per cent) of non-Irish national adults were separated or divorced, compared with 5.3 per cent of Irish. And while 3.3 per cent of non-Irish nationals were re-married following divorce, only 0.9 per cent of Irish nationals belonged to this category.
The figures also show a wide variation of marital status along class lines. The ‘Professional Workers’ category had the lowest rates of separation, divorce and widowhood, as well as an above-average proportion of singles.
Those in lower social classes were less likely to be married, and more likely to show up as single, divorced or cohabiting. However, category 3, ‘Non-Manual’ had a lower percentage of married than the ‘Skilled manual’, ‘Semi-skilled’ and ‘Unskilled’ groups.
The data also showed that there was a slowing in the decline in family size. Between 1991 and 2006, the average family size fell from 2.0 children per family to 1.4 children per family.
In 2011, while the average number of children had fallen slightly, it was still just below 1.4 children per family, representing a slowdown in the rate of decrease in family size.
The high number of births between 2006 and 2011 (73,000 per annum approximately) was a contributing factor in this slowdown.
The previous inter-censal period 2002-2006 had an average of approximately 61,000 births per year.
Rural families were larger on average than those in urban areas. The average number of children per family was 1.5 in rural areas, compared with 1.3 for their urban counterparts. Over 30 per cent of urban families had no children.
In rural areas this figure was 27.6 per cent. One-child families accounted for 30.2 per cent of the urban total, but only 26.5 per cent of the rural number.
Families with three or more children made up 15.5 per cent of the total in urban areas, and 21.1 per cent in rural areas
However according to the CSO, large families have not completely disappeared in Ireland.
There were 16,646 families with 5 or more children, of which 3,253 had 6 or more.