The Live Leaders Debate is hot at the moment, and the key question is: who should be invited?

As always, people are using a lot of selective data to justify why if Party X are there, then you have to invite Party Y as well because they’re doing just as well on Metric Z.

Naturally, we need to take a holistic approach using all available data to draw a fair and meaningful conclusion. The table below summarises many of the key metrics that determine how important a political party is:

From this we can see 3 natural line-ups:

1) Tories & Labour – the two largest parties and the two men most likely to be PM in May go head-to-head.

2) Tories, Labour, Lib Dems & UKIP – The Lib Dems largely get their invite from currently being in government, while UKIP’s success in the European elections and rise in Voting Intention place them in the Top 4.

3) Everyone – because then everyone’s happy. Or, rather, no one is…

Interestingly there is very little stochastic dominance – Conservatives, Labour and UKIP could all claim to hold the lead for the “most important” metric. Similarly, the Green Party are on par with the Lib Dems on many metrics, but the Greens lose out on arguments based around current political power.

And that’s why we’re going to see a lot of circular reasoning for why certain parties should or should not be present at the debates. If you see anyone using selective statistics to make politically motivated justifications, please send them this way. Hopefully they’ll then appreciate the importance to take in all available data at once, and not cherry-pick the bits that support their argument. Hopefully.

Appendix

“Score” is calculated by taking each party’s value for each metric and dividing it by the Conservative’s value, then taking an unweighted average across all available metrics. The “Currently in Government?” column is a binary 100% or 0% for Yes or No respectively. The table below shows calculations in full:

The 5 metrics used represent factors which determine how important a party currently is. If anyone has additional suggestions and data I’ll revise the analysis accordingly. For example, “Number of seats to stand in for May 2015” could be deemed highly relevant.

The 7 parties chosen are those currently invited to the debates.

Sources

http://www.parliament.uk/mps-lords-and-offices/mps/current-state-of-the-parties/

https://yougov.co.uk/news/2015/01/23/labour-lead-2/

http://www.parliament.uk/mps-lords-and-offices/government-and-opposition1/her-majestys-government/

http://www.bbc.co.uk/news/events/vote2014/eu-uk-results

http://www.parliament.uk/business/publications/research/briefing-papers/SN05125/membership-of-uk-political-parties

http://blogs.spectator.co.uk/steerpike/2015/01/heres-why-nobody-has-been-able-to-verify-the-green-surge-numbers/

(Note that the Green Party membership numbers are more recent than others)