Public Affairs

Census explained

In March, the CSO will begin publishing nine volumes and two profiles of census information. Stephen Dineen talks to Deirdre Cullen and Gerry Walker, two of the CSO’s senior statisticians overseeing the entire Census 2011 process.

“What’s unique about the census,” says Deirdre Cullen, “is that it hits every single person in the country.” Cullen is responsible for census recruitment, publicity and outputs. The 2011 census project began in September 2008 and will conclude with the final data publication in December 2012. Intercensal information queries are ongoing and planning is already underway for the 2016 census.

At the outset, the CSO carried out a public consultation (over 90 submissions were received) and wrote to government departments, agencies and other organisations to gauge what should be included in the census.

Previously the census used the electoral division as a basic unit for enumeration. However, household numbers vary from fifty to 35,000, therefore the CSO, in collaboration with Ordnance Survey Ireland and the National Institute for Regional and Spatial Analysis (NIRSA) in NUI Maynooth, designed a small area unit (approximately 90 households) for the 2011 census.

The recruitment process involved 15,000 job applications. All applicants were interviewed (and successful candidates signed-up) on the ground working and paid within seven weeks. “We used the people that we recruit first to interview the next layer down, so by the time we have the 440 field supervisors in place we use them to interview for the enumerator job,” says Cullen.  4,854 enumerators covered 19,760 small area units.

Several questions distinguished the 2011 form from that in 2006. Blindness and deafness were included as individual disability categories. The household occupancy and home heating questions were changed and a question on general health, used in the UK census, was added. Cullen says the question (“How is your health in general?”) has been found to be “an excellent indicator of actual health of the population.”

Before the field work, enumerators were given a 130-page manual as part of their training. “We try to cover every eventuality in that manual, so there’s no doubt or ambiguity as to how things should be done,” says Walker, who is responsible for field operation, geography and processing.
There were 10 weeks of field work, five before census night and five after. The collection process encountered difficulties such as the sensitivities of certain groups to answering particular questions (such as the question regarding the number of children born alive) and the 6,000 out of 1.8 million forms that were not filled in despite persistent calls. There was also some hostility from some households. “Particularly this time,” explains Walker, because of “all of the anti-public sector stuff in the press, our enumerators would have been knocking on doors and they would have got doors slammed in their faces.” Cullen states, however, that “by and large our experience is the Irish public are very co-operative with the census.”

The actual census forms were scanned in a processing system with up to eight stations (e.g. one for numeric questions, another for family coding) and software used to assist with problematic coding. Credibility checks were performed. “There are about 400-500 different credibility checks that we do on a census form,” explains Walker, “so we’d be looking at things like a working airline pilot that has ticked that they were blind.” The CSO operates on a general rule that data is not amended unless it’s absolutely clear to be wrong.

This year’s output design will also differ from the previous census. “We’re going to do a lot more interpretation and telling the story of the results than was done before,” explains Cullen, adding that there will be charts, maps and graphs and it will be more colourful. “The idea is to make it much more accessible to the public, much more user-friendly.” There have been over 65,000 views of the preliminary census report web page.

Whereas small population profile information was presented thematically before, 2011 information will be presented in two-page (A4) documents, with all the information on a town in a written report without tables. Working with NIRSA, the All Island Research Observatory resource will be used to display census data on maps. 

Preliminary results

Housing stock and preliminary population figures were published in June 2011. The big surprises were the higher than expected population level (90,000 more than expected), the big increase in the number of vacant dwellings (by 10.5 per cent) and that two constituencies had exceeded the population threshold of 30,000 (Laois-Offaly and Kildare South). On the higher than predicted population total (4,581,269), Cullen says: “We’ve continued to have immigration in Ireland, possibly higher than what the estimates had shown over the intercensal period.” And while “the gap isn’t quite as bad as it looks,” the CSO will now revise the population estimates (derived from the Quarterly National Household Survey) from previous years to account for the discrepancy.

A range of state agencies, interest groups and voluntary organisations will use the census data. An Garda Síochána, for example, will use it to profile the level of deprivation in areas. The private sector uses it to profile areas to make business cases for foreign direct investment, using information such as the number of graduates in an area.

As for the future format of the census, Cullen states that the role of administrative records should be examined to see “whether or not we can use it, if you like, to back-fill gaps in data.” She adds: “We certainly need to think about the internet option. We need to think about posting out and receiving data back by post.” In the UK the Office for National Statistics is considering alternatives to the traditional census for 2021.

Whilst most countries perform censuses every ten years, Ireland’s tradition of five-yearly censuses is justifiable, according to Cullen, “because of the nature of our population and how it changes,” and the speed at which it is growing.


Census information publication schedule

29 March:  Principal demographic; results volume
26 April: Population classified by area volume; geography profile
24 May: Ages profile
28 June: Principal socio-economic; results volume
26 July: Workers and employment profile
30 August: Housing profile
20 September: Households, families and marital status profile
11 October: Migration and diversity profile
1 November: Disability, carers and health profile
22 November: Education profile
13 December: Commuting profile
To be confirmed: Small area population; statistics web tables

Counting in numbers
€50 million
1.8 million forms
19,760 small area units
4,854 enumerators
300 tonnes of census forms

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