Thursday, May 11, 2017

The Election Dot Map

In just under a month's time the UK will hold yet another general election.

After the last UK election hexagonal grid maps seemed to be the most popular way to visualize the results. The use of hexagon grids helps to overcome the problems of political districts being based on equal population areas and not on equal geographical areas. Using hexagon grids stops an election map being visually overwhelmed by the results in those rural areas with geographically larger constituencies.

However one problem with a traditional grid map is that it only shows which party won each constituency and not the number of votes cast for each party in each constituency. Culture and Insight has attempted to address this problem by creating a dot map of the 2015 UK election results. The Colours of The 2015 Electorate map attempts to provide a better visualization of the number of votes cast for each party within each constituency by representing voters with colored dots.

Each colored dot represents one hundred voters for that political party. The location of the dots is randomized within each constituency.

You can click on an individual constituency on the map to view which political party won the seat, who came second and the size of the winner's majority. Although the stated purpose of using a dot map is to 'visualise (the) diversity of voting' in each constituency clicking on the a constituency doesn't reveal the number of votes cast for each political party.

Another way to show the number of votes cast for each party within each constituency is a 3D hexagonal cartogram. For example this Brexitogram map, showing the results of the UK referendum on the EU, allows you to see the number of votes cast for each side. The height of each hexagon represents voter turnout.

The disadvantage of such an approach is that you can only really see both colours in the stacks around the edge of the map. In election districts that appear in the middle of the country you can often only see the top colour. The map partly overcomes this problem by allowing you to turn the colours on & off. This allows you to at least view the results in much the same way as a more traditional 2D hexagonal cartogram.

There are advantages and disadvantages to all these approaches to visualizing election results. On the morning of the 9th June broadcasters & newspapers will want maps which best visualize the overall results in each constituency. They are therefore most likely to use a traditional choropleth or 2D heagonal cartogram map. A map that best visualizes the overall winner in each election district and in the whole country.

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