Turnout in May’s Assembly elections was 45.3%. Higher than in 2011 but considerably lower than UK general elections (66.4% in 2015, since you asked). Does this lower level of enthusiasm hit all parties equally though?
Below I’ve made boxplots of the difference between the number of votes each party got in the Assembly election and the Westminster election in each constituency. Negative scores are lower votes in the Assembly and positive are higher.For those of you unfamiliar with boxplots (a not unusual state of affairs):
- The black line in the middle is the median – the datapoint exactly in the middle.
- The coloured bit is the interquartile range – the gap between the 25th percentile and the 75th percentile. So the middle 50% of observations fall here.
- The ‘whiskers’ go out as far as the outlier 1.5 times the interquartile range.
- Other outliers appear as the little dots.
Anyway, here it is:
Everyone except Plaid Cymru generally does worse in the Assembly elections – indeed Labour, the Conservatives, and UKIP don’t do as well as well in the Assembly election (in terms of number of votes) as they do in Westminster in any of the 40 constituencies. The Liberal Democrats generally do a bit worse, but do better in a few seats. This could be related to their pronounced concentration of votes in just four constituencies – locally competitive parties draw tactical voters.
The interesting exception is Plaid Cymru, who do better in the Assembly in 26/40 seats. This could be for a number of reasons:
- The Westminster-based parties (yes, you too UKIP) have other fish to fry and this might translate into less organisational focus on Assembly elections.
- People who vote for the Westminster parties could have less enthusiasm for the assembly elections than Plaid voters.
- Some people might vote for Plaid in the assembly but for another party in the general election.
Plaid’s advantage here, it is important to state, is not just a relative one. They don’t just suffer less than other parties from the lower turnout, they actually outperform their Westminster results. This means that Option 1 above cannot be the whole story.
My last few posts on the predictive power of Westminster results on Assembly results suggest that it might be possible to build a fairly good predictive model for Assembly elections using Westminster results. The parties’ relative abilities to turn out their vote in the Assembly elections is an important parameter to include in such a model.
Next on Cyfri am Byth: a first draft of a model…