There has been a lot of fairly wild speculation in recent years about the rapidity of changes in the religious composition of the population of Northern Ireland. Even as late as a few days ago there were fresh stories in the press about an alleged major shift in the population balance in favour of the Catholic minority.
The census data published on Thursday has given us for the first time in many years a clear and unchallengeable picture of the scale and pace of these changes.
In addition to the data on religious adherence this census also provides new information about the religious background of the population. We now have a better fix on the relative strength of the two communities in Northern Ireland than has been available at any time since 1961.
For, during the whole of the past forty years the growth in the number of people stating at census time that they have no religion, or refusing to state their religion, has made it increasingly difficult to assess accurately the political implications of a changing religious balance.
The table below sets out the results of this census, and of those of 1961 and 1991. The intermediate censuses in 1971 and 1981 were both distorted by political factors. The new data about people's religious background is especially valuable.
While there remains just under 3 per cent of the Northern Ireland population who not merely deny any religious adherence but also refuse to admit to any religious background whatever, it is clear that the vast majority of this small group actually have a Protestant background.
In a number of predominantly Catholic areas less than 1 per cent claim to have no religious background, whereas in overwhelmingly Protestant areas this percentage is typically 4 or 5 per cent. Consequently it is possible to say with certainty that the percentage of people in Northern Ireland with a Catholic background is now about 44.5 per cent. And that is a good deal lower than some propagandist stories had been claiming, for figures of 46 or 47 per cent of Catholics have been confidently claimed by some triumphalist republican sources. At what rate has the Catholic percentage of Northern Ireland's population been rising? The figures for religious adherence would seem to suggest that the Catholic percentage of the population rose by less than 2 percentage points in the past decade. But in fact, when allowance is made for the probable religious background of people who in 1991 stated they had no religion or refused to name their denomination, the actual increase in the Catholic share of the population may have been slightly higher than this, at just over 3 per cent.
That is a somewhat higher rate of change than the average increase of 2 per cent per decade in the preceding thirty years. . However, although about 44.5 per cent of the Northern Ireland population now come from a Catholic background, account must be taken of the fact that during the 1980s and the first half of the 1990s there were more Catholic than Protestant births - a situation which may, however, recently have been reversed with a decline in Catholic fertility towards the Protestant level.
This means that just over half of those under 18 are Catholic: consequently the proportion of those over 18 - the electorate - coming from a Catholic background is still only 42 per cent.
In view of the fact that the share of votes cast for nationalist or republican candidates in last year's Westminster election was 43 per cent, and given that some people of Catholic background also vote for Alliance candidates, this indicates that in that election, as in other recent votes, the turn-out by people of Catholic background has been somewhat higher than voters from a Protestant background.
Even if one assumes, improbably, that in the decades ahead births to people with a Catholic background continued to equal or slightly exceed the number of births to people of Protestant background, an electoral extrapolation from the present situation, allowing for the increase in the percentage of people of Catholic background that will occur in older age groups as the present young population moves up the age scale, suggests that equality between the two electorates would be unlikely to be reached until about the year 2030.
This date could, however, be brought forward somewhat if there was a continuance of the tendency in the 1990s for a greater number of Protestant young people to go to Britain for higher education, and to remain there. But it is, of course, totally simplistic to equate religious background in Northern Ireland with preferences for Irish or British sovereignty.
In a series of public opinion polls throughout the past decade a significant proportion of voters of Catholic background - about 35 per cent until the Belfast Agreement, but a lesser proportion since then - have expressed a preference for remaining in the United Kingdom, and, of course, there has never been a balancing willingness by any significant number of people of Protestant background to contemplate Irish unification.
The 15 per cent to 20 per cent of Catholics who still prefer to remain in the UK may well be influenced in their thinking by a recognition that an Irish State, having only one-fifteenth of the wealth of Britain, would be unlikely to be able, or willing, to sustain the scale of financial transfers that Northern Ireland currently receives from Britain to compensate it for the weakness of the Northern Ireland economy. These transfers are on a scale that allows Northern Ireland, where output per head is now over 20 per cent lower than in this State, to enjoy living standards that are some 5 per cent to 10 per cent higher than here - and that is something that people would not easily give up.
For a majority in favour of Irish unity to emerge even a quarter of a century hence it would be necessary not alone for the Catholic fertility rate to remain much higher than that of the Protestant community but also for a further major shift in attitudes to Irish unity to take place amongst people of a Catholic background - or less probably, within the Protestant community.
The truth is that the prospect of such a development is at present sufficiently remote for it to be irrelevant to Irish politics in the foreseeable future. At best it might be a matter for our grandchildren to deal with.
It is, therefore, unfortunate that propaganda efforts suggesting that Irish unity by agreement is likely to take place within the next fifteen years should at this time be arousing new, and quite unrealistic, fears amongst a unionist community that has already been emotionally destabilised by the scale of the political changes it has had to face in recent times.