The recent publication of the detailed Vital Statistics for 1995 provides the material for 15-year comparisons with 1965, just before our demographic revolution started, and 1980, in which both births and marriages peaked.
During the three decades since 1965 we have experienced several distinct demographic revolutions, which together have profoundly changed the character of our society. The first of these involved a halving of marital fertility. As a result, by 1995, despite the fact the number of women of childbearing age was by then two-thirds larger than in 1965, one-third fewer babies were being born.
In parallel with this, but starting somewhat later, in the mid-1970s, there also came about a huge change in our marriage pattern. A quarter of a century ago two-thirds of women who married did so before the age of 25. Today, however, barely a quarter marry before that age.
A corollary of this shift away from early marriage is that the number of women marrying at 25 or over has increased by over two-thirds. But, even though the number of women of marrying age is one-third higher today than in 1975, a drastic shift in the age pattern of marriages has produced a net fall of one-quarter in the total number of marriages.
Much of this decline may well have been accounted for by a postponement of marriage, rather than by an actual abandonment of it. Thus, between 1975 and 1995 the commonest age for weddings rose by five years, from 21-23 to 26-28 in the case of women, and, despite the sharp fall in the marriage rate since 1975, the total number of marriages by women in their thirties is now twice as high as 20 years ago.
There may well be a "biological clock" factor at work here. For it is, I think, significant that by 1995 the number of marriages of women aged 29-32 had moved somewhat out of line with the pattern of marriages at both younger and older ages. This suggested some kind of a bulge at that particular age level which is the age at which it is believed women who have postponed child-bearing tend to review their attitude to the issue.
Since 1995, the last year for which such detailed statistics are available, the decline in the overall marriage rate seems to have stabilised. Although there have been some minor fluctuations in the total number of marriages, since then the figure has oscillated around 16,000 a year.
Nevertheless, even if postponement of marriage provides most of the explanation for the fall in the marriage rate in the years to 1995, it now seems very unlikely that women born since 1970 will have the same experience as those who were born in the 1950s - over 90 per cent of whom eventually married.
In a State in which the size of the young population - those in their 20s and 30s - has risen in recent decades by more than two-thirds, an inevitable consequence of the drop in the marriage rate has been a very large increase - a doubling in fact - in the number of single young people.
Even if there had not been a shift in attitudes towards extramarital sex and single parenthood, this very large increase in the actual number of young single people would have increased substantially the number of non-marital births. But by 1995 there had also been a quadrupling of the non-marital birth rate . . . As a result, by that year almost one-quarter of all births were non-marital - a proportion that has since risen to 28 per cent. That 20-year period also saw a big increase in the number of abortions on Irish women in Britain. By 1995 such abortions were running at more than 4,000 a year. As it is reasonable to assume that the vast majority of these abortions involved single women, it would appear that by 1995 about one-quarter of all non-marital pregnancies were being aborted.
Non-marital births used to be commonest in the 20-25 age group: indeed in 1965 the non-marital birth rate tapered off fairly steadily from age 25 onwards. But by 1980 this decline was starting at a slightly later age. And by 1995 the non-marital birth rate remained at much the same level - between 3 per cent and 4 per cent - across the whole of the age spectrum from age 19 to age 39.
This new phenomenon seems to reflect the fact that non-marital births are no longer just the product of casual sex or of unstable relationships between young people. Whereas, in the past, most cohabiting couples tended to get married when a child was on the way or even when they decided to have children, it would seem that a not insignificant minority of such couples now regard marriage as an unnecessary preliminary to parenthood either in their twenties or in their thirties.
Nevertheless, it would seem that many women who have a non-marital child or children do later get married - although not necessarily to the parent of their child, or children. This conclusion can be drawn from the fact that while in the 18 years to 1996 some 120,000 non-marital children were born, in that year the number of dependent children in respect of whom Lone Parents' Allowances were paid was barely 80,000. And, allowing for the fact that some of these payments may have been sought and made despite the subsequent marriage of the claimant lone parent, and that others will have been claimed by lone parents with younger children who in 1996 had yet to marry, it would seem that a substantial proportion - probably over half - of lone parents eventually got married.
Until recently the rising number of non-marital births was paralleled by an even more rapid decline in marital births. But since mid-1996 this latter decline has been halted: in the period of over two years after June 1996 the number of marital births actually rose by about 4 per cent. We do not, however, yet know any details of this recovery - such as the age group of the mothers responsible for this rise in marital birth rate.
A consequence of the - mainly non-marital - increase of one-tenth in the birth rate during the past four years has been that the natural increase in the population - the excess of births over deaths - has risen from 17,000 to 21,000. But, even at this higher level, the natural increase in the population in the 12 months ended March 1998 was overshadowed by the somewhat larger figure for net immigration, which thus accounted for over half of the population increase during that 12-month period.
Between them, these two factors boosted our population in that 12month period by almost 45,000 or 1.25 per cent - the biggest annual population increase of the past two decades. And it seems probable that a similar population increase during the past 12 months has now brought the population of the Republic up to 3.75 million - a figure which is one-third above the low point of 1961, and which brings our population back to the level of the early 1880s.
Future population trends depend on the extent to which this recent flow of immigrants, both returning Irish and non-Irish, continues in the years ahead. But if the flow of external industrial investment is maintained, and if housing is available at a cost level acceptable to immigrants, our population could continue to grow at well over 1 per cent a year - which would bring our population up to four million within the next five years.