Mr. Pádraig Dalton:

It is certainly potentially one of the explanations but we do not have access to the data source being used by the Department, nor are we familiar with its methodology. We are not really in a position to comment on the differences between its figure and ours. All we can say is the 33,000 figure excludes vacant dwellings built between 2011 and 2016, and there are also 114,000 households where we did not get information. It would be naive of us to assume none of those was built between 2011 and 2016. That captures some of the Deputy's questions. The Deputy answered the social housing issue himself. It is a self-completion question and if a householder is in receipt of support, perhaps from the State, he or she may well describe himself or herself as living in social housing. It is very difficult for us to determine how the householder perceived that particular status. It could be part of the difference between the two. I do not know if the overcrowding issue is in line with the legislative requirement. Perhaps the other witnesses know but if we do not, we can come back to the Deputy on it.

Senator Coffey mentioned the sharing of data. The Central Statistics Office shares data but only at an aggregate level. We never provide information at an individual level, whether it relates to an individual household or person. It is important to put that on record. One of the principles of the office is equality of access. As a result, everything we publish we put into the public domain so it is accessible for absolutely everybody to research. We do that through the StatBank and small-area population statistics. It is there for all, including planning authorities, etc., to see. We engage with the Housing Agency and the local authorities and we receive many demands from a broad range of institutions that would be involved with a broad range of policy issues and not just housing; they would take in health and education as well. We undertake bespoke analysis and, again, the date is at aggregate level for those. If we feel it is in the public interest, we can put data into the public domain and we do so in many cases.

We do a lot of bespoke analysis and have been doing that since before I joined the CSO, which was 26 years ago. We share data but only at an aggregate level.

Mr. Halpin will answer the question on whether vacant dwellings are connected to public services and whether they are habitable or uninhabitable. There is a clear shift from rural to urban living, which has been going on for a number of years and on which we published details in the censuses of 2016 and 2011.