Levels of variance per Dail constituency based on definitive Census 2011 population figures

Adrian Kavanagh, March 29 2011

The definitive Census 2011 population figures have been published today. Election boundary changes (for general and European elections) will be made on the basis of these, but this time are taking place in the context of a decision by government to advise a reduction in Dail seat numbers by between 6 (160 seats) and 13 (153 seats). So what do these population figures mean in terms of which constituencies may, or may not, be likely to have their election boundaries changed following on the upcoming Consituency Commission report, especially given that this body effectively will have eight different options in terms of total Dail seat numbers to choose from? The following document, which outlines the degree to which each constituency’s population per TD ratio will vary (in percentage terms) from the state average for each of the different seat number options open to the Commission, should help in regard to this.

Extent to which constituencies’ population per TD ratios vary from state average for different seat number options (and likelihood of boundary changes being made to these – as highlighted in yellow/blue)

What is evident from this analysis is that the main driver of change in relation to the redrawing of Dail election boundaries this time will probably be more so the decision to reduce Dail seat numbers over and above those changes required by differential levels of population change within the state. Had the number of seats remained at 166, changes to constituency boundaries would have been absolutely necessary in just 12% of cases (where level of variance exceeds 7.89%) and would have been probable in a further 21% of cases (where level of variance exceeds 5% but not 7.89%). When you are faced with a 160-seat option (the largest option open to the Constituency Commission), changes to constituency boundaries would now be absolutely necessary in 23% of cases (where level of variance exceeds 7.89%) and would be probable in a further 26% of cases (where level of variance exceeds 5% but not 7.89%). The level of changes required further increases in line with decisions to reduce Dail seat number by even higher levels and for a 153-seat option (the smallest seat number option open to the Constituency Commission), changes to constituency boundaries would now be absolutely necessary in 49% of cases (where level of variance exceeds 7.89%) and would be probable in a further 23% of cases (where level of variance exceeds 5% but not 7.89%).

One interesting point to note is that if the population increase between the 2011 Census and the next census in 2016 proved to be exactly the same as that between 2006 and 2011 the population in the Republic of Ireland would then stand at 4,965,286. Given the requirement in the Constitution that there be one TD for every 30,000 people (a factor that limited the possible reduction in Dail seat for the 2011-12 Constituency Commission revision to a range between 6 and 13, as the smallest number of Dail seats you can have with a population of 4,588,292 is 153), the smallest number of Dail seats that the Commission would be able to choose in the next revision would be 166 based on aprojected 2016 population figure of 4,965,286, which of course is the current seat level in Dail Eireann.

It is also worth noting that based on the cubic root rule, the idea parliament size for a population of 4,588,292 would be…166 seats.

Given the impressively small level of variation between the provisional (based on enumerator returns) and definitive population figures for the constituencies, my earlier posts (which were based on the provisional figures) as to what might happen in relation to decisions to be taken by the Constituency Commission in relation to changes to Dail election boundaries still largely hold true. But I have updated these to take account of the newer, and definitive, Census 2011 population figures. A more detailed version of this post may be viewed at the Ireland After NAMA blog.

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About Adrian Kavanagh

Lecturer in Maynooth University Department of Geography.
This entry was posted in Census2011 definitive figures, Constituency Commission, Constituency information, Election boundaries and tagged , , . Bookmark the permalink.

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