Where Ireland splits in half

I have been using spatial data with clients a lot recently. Visualising the distribution of services or service users can unlock knotty strategic questions in ways that people find simple and intuitive. In the process, I have become familiar with Ireland's many helpful open data resources, including our population data.

Amongst the researchers demonstrating the value of visualising spatial data is UK geographer Alasdair Rae, who shares many interesting map vizzes on social media, including population balance points in the UK (with which he seems to be slightly obsessed). Inspired by this striking visualisation which he shared on Linkedin, I took a look at Republic of Ireland data to see where our own population median might be.

I focused on an east-west axis for Ireland. Using Census 2022 Small Area data, the dividing line for our population falls at around 7.08° west. The line runs through the eastern Midlands, close to towns such as Edenderry, Portarlington, and Tullamore. It passes directly through University Hospital Waterford. An equal 2.6m people live on either side of the line.

The contrast with land area is stark. While roughly half of Ireland’s population lives east of this line, that eastern half accounts for only about 19% of the country’s land area. The remaining 81% of land lies to the west, home to the other half of the population.

It would be interesting to examine how this dividing line has moved over time — whether drifting east or west — and whether the populations on either side differ in meaningful ways. These are questions I hope to return to in future.