The data recently published from last year's census makes it possible to get an accurate fix on the scale and momentum of marriage breakdown in recent years. However, in assessing the scale of marriage breakdown, the data in respect of women are to be preferred.
The figures in respect of men always tend to be lower, partly because some at least of the men whose marriages have broken down have emigrated, leaving deserted wives behind, but also perhaps because men may be less willing than women to disclose on the census form their true marital situation.
In last year's census just under 28,000 women stated that they were divorced, either here in Ireland in recent years, or elsewhere. Of these, fewer than one-third had re-married. Just twice as many, 57,000, are separated.
Of the total of 960,000 women who have been married, 15 per cent are widowed (of whom only a very small number have remarried), and about 9 per cent have experienced marriage breakdown. That leaves about three-quarters of women who remain married.
The highest rate of marriage breakdown is among those who are now in their late 40s. One in seven women in this age cohort have already had this experience, and unfortunately others will experience marriage breakdown later on, when in their 50s or 60s.
From the pattern of breakdown at different ages recorded in recent censuses, it is possible to predict now that for this age cohort the ultimate breakdown rate is likely to be rather less than 20 per cent. However, for younger age groups, among whom the breakdown rate is already higher than it was at their age in the case of those somewhat older, the prospect is for an eventual breakdown rate above 20 per cent, but almost certainly below 25 per cent. That would be less than half the British marriage breakdown rate.
Moreover, with about six years' experience of divorce behind us, it now seems likely that in Ireland the proportion of marriage breakdowns that lead to divorce is also going to be lower than in Britain. Since divorce was legalised here the number of divorces granted annually has gradually drifted up to about 3,000 a year. But the proportion of marriages likely to end eventually in divorce seems unlikely to rise much above 15 per cent, and it will take a number of decades for that figure to be attained.
Such a divorce rate would be in line with the estimate I gave at the time of the 1986 divorce referendum (which I based on the divorce rates for Catholics in Northern Ireland and in southern European countries) and is, of course, very much lower than the alarmist forecasts made by some of the opponents of the divorce lobby 17 years ago.
This recent census has also yielded data on the current scale of cohabitation without marriage. In 1996, when the census form asked the relationship of members of the household to whomever had nominated himself or herself "Head of Household", one of the responses offered was "Living together as a couple".
Because that rather bluntly-phrased question may have secured an incomplete response, in last year's census the question was changed to whether another member of the household was a "partner" of the self-nominated household head.
Together with the impact of changing public attitudes to cohabitation since 1996, this modification in the form of the census question may have had some effect upon respondents' willingness to admit to being in this situation, and these two factors may partly account for the 125 per cent increase in cohabitation recorded during this six-year period. Part of this increase is also explained by a significant rise in the total number of households, including households with couples.
Last year's census shows that just under 10 per cent of couples are now cohabiting rather than married. But, for the reasons just given, the fact that this is just twice the 1996 ratio of 5 per cent may exaggerate the rate at which cohabitation has been increasing.
Three-fifths of cohabiting couples have no children under 25, as compared with barely one-third of married couples, and less than 4 per cent of children have cohabiting parents. This contrasts strikingly with the surprisingly high proportion of young people under 25 who have been, or are currently being, brought up by lone parents. Such young people constitute 19 per cent of the total of the almost 1.5 million people under that age.
This reflects the fact that the Irish proportion of extramarital births is now l0 per cent higher than the average for the rest of the EU.
To some extent this may be accounted for by the domestic availability of abortion in most other member-states, but as even five years ago more than one-quarter of all Irish non-marital pregnancies - including three out of every eight first non-marital pregnancies - were aborted, the absence of domestic abortion in Ireland may not be having as much effect upon our non-marital birth rate as might have been imagined.
A very striking feature of Irish demography has always been the high average age of women at child-bearing, but in the 1960s and 1970s, when early marriage became more prevalent in Ireland, this average age declined more rapidly here than in other EU countries, Greece and the Netherlands excepted.
However, in the 1990s the high employment participation rate of young Irish women had the effect of raising to 28 the average age at which Irish women have their first child. And, whereas in 1980 less than one married woman in seven postponed having their first child until they were in their 30s, by the year 2000 this proportion of later first births had risen to over half of the total.
The drop of over one-third in the birth rate after 1980 has, of course, been sharply reversed during the last eight years, the number of births having increased since 1994 by over 25 per cent. Contrary to what some believe, only a quarter of this increase is attributable to asylum-seekers; the bulk of it being accounted for by a big increase in births to Irish women in their 30s.
It is thus clear that an important part of the drop of almost 40 per cent in the birth rate between 1980 and 1994 simply reflected a postponement of child-bearing by women in their 20s, who may have preferred to remain at work during that earlier part of their adult life, or who, with their partner, may not have been able to accumulate a deposit for house purchase.
The recent big jump in births to women in their 30s may also have reflected a "biological clock" effect.
There has also been a big jump in the marriage rate, which since 1995 has increased by almost one-third to 20,000 a year, a figure not seen since the early 1980s. This, too, seems to reflect in significant measure a decision by women to postpone marriage.
However, because of the deplorable failure of the Registrar General's office during the past six years to supply to the CSO any data on the age of spouses at marriage, it is not possible to be more precise about this important aspect of our recent demography.