There have been many great interactive maps and graphics produced for the 2015 General Election. A map I haven’t seen though is one that attempts to show the relative strength of support for each party in each constituency. This is what the map above seeks to achieve. The principle is simple – you have 3 buckets of paint – one red, one green, one blue – and you mix them together based on the vote share of each party. So a strong Conservative win gets lots of blue paint and relatively little from the other two, whilst split in support across parties will result in a more muddy colour as all three paints get mixed together in similar amounts. As an extra step I also rescaled the size of each area by the number of people who voted there to help show cities, especially London, more clearly.
Of course, this map falls a little short of revealing the most interesting results of the election since they mostly occurred in the green areas. A swing from Lib Dem to SNP, for example, would still warrant mostly green paint since both parties fall in the “Other” category. Instead, I see it as a useful way of showing where support for the Conservatives and Labour was strongest as well as those areas where the results underlying the outcome of the election were far from definitive.
I’ve included individual maps below showing how each of the colours are combined to produce the final map.