These days, in his capacity as a researcher with the ESRI, Professor John FitzGerald uses information gleaned from the census on an almost daily basis. It's absolutely crucial. It's central to the work of transport, education, finance . . . in predicting pension needs . . . health, where old people are living. You can't get the level of detail that we get from the census in any other way and the applications for the information are extremely far-reaching.

For example, the census will tell us how far children travel to school. That's important for the ESRI, who are interested in the arcane and the ridiculous, for the local authorities, for the departments of education and transport and even the department of health. We will all use that."

When the results are crunched and cogitated later this year, they are likely to show an Ireland more radically altered since the last census, in 2002, than between any other head-counts in its history. Already, the CSO predicts that the new census will reveal that almost a quarter of a million houses in Ireland were vacant this weekend (and not just because of the Flight of Munster). The increase in the number of empty holiday homes has been enormous, says the CSO's Brian King, who believes that will be ?one of the stories of census 2006".

The other is perhaps more obvious: one of three new questions on the census form concerns ethnicity and gives an indication of the shape and colour of the Ireland the CSO expects to emerge from the 1.28 million forms that will be filled in tonight. Although the form is available only in English and Irish, for the first time, the accompanying guide to households has been printed in 12 different languages. Leaders of non-national organisations and groups have also been contacted by the CSO in advance of the census in an effort to ensure that everyone who lays their head in Ireland tonight will understand that they must appear on a form. A combination of the influx of non-nationals and a massive increase in the apartment-dwelling population has ensured that the distribution of the census forms has presented a greater challenge than ever before. ?We've been getting feedback that there are problems out there, " Brian King of the CSO said on Friday. ?Apartments are a concern. We do try to contact management companies where possible, but it is difficult to make personal contact with every apartment-holder."

One enumerator reported that some people in apartments have been hiding inside in the mistaken belief that the knock on the door was from the television licence inspectors.

If people don't want to open the door, there's very little we can do. If people want to hide, it is difficult. But we do stress that the information on the census is for statistical purposes only. And we do want to count everyone, " says King. By Friday evening, in households where contact still hadn't been made, enumerators were permitted to drop the census form through the letter box along with a covering letter . . . though the CSO maintains that in these cases, the enumerators will still try to follow up with contact right up until tonight's deadline.

The other two new questions on tonight's form concern fertility rates . . . women will be asked how many live children they have given birth to . . . and employment. The latter question is designed to measure whether non-nationals are getting jobs commensurate with their educational qualifications. Like all the questions on the census, its language has been carefully engineered to ensure that the information given is of optimum statistical use. FitzGerald recalls a question in a recent census concerning emigration, where the figure of net emigration suggested by the census was only one-third of the true figure. Parents filling in the census didn't want to admit that their children had emigrated; they preferred to think they were just away for a while. So they had to change the way that question was asked. Language is very important."

But some languages, it seems, are more important than others. In spite of the CSO's recognition of the enormous non-national community, none of us will be asked tonight if English is our first language. ?It probably should be there, " says King, but we did engage in a long consultative process and it simply didn't come up. I'd imagine it will be on the next one."

FitzGerald regrets that there isn't a specific question about language . . . ?aside from the one about Irish which is always problematic" . . . but he still welcomes this new census. Hell, he relishes it. Having never quite gotten over his omission from the 1971 population count, he's taking no chances tonight. I'm making sure I'm in the right place. I'm not going to travel at all."