Decision trees for UK voting

The next data-analysis method I'm playing with is decision-tree regression.

It's a method often said to be included in a field of statistical computing (called machine learning, statistical learning, artificial intelligence, data mining, supervised learning, etc). Decision trees usefully split up datasets into groups, often using YES/NO questions at each split.

I'm using data from Qriously (date 2017-06-07) in the run-up to the UK general election. I'm looking only at England & Wales, and I've only considered 3 regressors: gender (0=F, 1=M), age, income. I've considered a YES/NO voting intention for the 5 biggest political parties.

The trees are below. Here are some key aspects that jump out:

• Age seems to be the most important regressor for most parties.
• CON seems to get many votes from older voters (except if they're poor).
• CON gets few votes from younger votes (especially poorer voters).
• CON's best group were older females (not males as one might expect - maybe this is simply a bias of longer life expectancy for females).
• LAB/CON results are fairly inverted (as we might expect), i.e. poorer and younger voters favouring LAB. 
• LAB's best group were young, poor females.
• LAB's worst group are the 65+.
• LIB seems to do best from low- and middle-income voters, more-so for male voters.
• LIB's two worst groups are from (a) elderly richer females, and (b) poorer older voters.
• GRN's voters are generally younger (the one exception being wealthier older females) -- young males is one key group.
• GRN does badly with (a) older, poorer voters and (b) older, richer males.
• UKIP voters are generally poorer. One key group being poorer younger males.

There are so many assumptions and drawbacks in these sorts of analyses - but anyway, interesting all the same.

CON: 

LAB: 

LIB: 

UKIP: 

GRN: 

UK general elections - progressive alliance?

Another UK general election is coming. Again in the media a so-called progressive alliance is being talked about (e.g. Guardian). The background is that in the UK in general the conservative-right has normally held together in one party, whilst the liberal-left has been fragmented. And in a winner-takes-all voting system, the liberal-left has been badly hit over the years - but I want to know HOW badly.

Normally in the past it has simply been a case of Labour + Liberal (Democrats). Although these days one could probably add in other parties to the mix, like Green and maybe say SNP, Plaid Cyrmu, etc.


So, in 18/19 general elections, progressive parties received the largest vote share -- although there was a Conservative government in 9/19 cases and a Conservative-led government in 1 case. So this confirms in numbers that the voting system favours the Conservatives.

It is rare for the progressive parties to even go below 50% - e.g. it happened in 2015 presumably because (a) the LibDems were punished for going into a coalition with the Conservatives and (b) UKIP's vote-share rose lots (and it seems that UKIP has a mix of right-left-conservative voters).

EDIT: Andy requested the seat info too, so here it is: