May 7th, 2010


An odd result

In our area, the Lib Dems gained a seat, going from 3 to 4. But the odd result is the seat they won: Norwich South.

Look at those figures:
Simon WrightLiberal Democrat13,96029.4-0.6
Charles ClarkeLabour13,65028.7-8.7
Antony LittleConservative10,90222.9+1.1
Adrian RamsayGreen7,09514.9+7.5
Steve EmmensUK Independence Party1,1452.4+0.9
Leonard HeatherBritish National Party6971.5+1.5
Gabriel PolleyWorkers Revolutionary Party1020.2+0.0

Yes, the Lib Dems actually gained a seat while losing share. What happened was that Labour lost many more (with an appreciable number going Green), letting the LDs in.

(East England is pretty solid blue. Tories: 52. LDs: 4. Labour: 2 (the two Luton seats, with control freak Esther Rantzen failing).

Why the Swingometer needs to be retired

Look at the following table:

Oliver HealdConservative26,99553.5  +5.5
Hugh AnnandLiberal Democrat11,80123.4 +3.1
David KirkmanLabour8,29116.4-11.9
Adrianne SmythUK Independence Party2,0754.1 +0.8
Rosemary BlandGreen8751.7 +1.7
Richard CampbellIndependent2090.4 +0.4
David RalphYour Right To Democracy Party Limited1430.3 +0.3
Philip ReichardtIndependent360.1 +0.1

Yes, this is a case where the leading candidate increased his vote, the former second place collapsed into third place, and the previous third place rose to second place.

So how does the Swingometer report this multifaceted situation?

A 1.2% swing from LD to CON.

So how is this calculated?

It's half the difference in the winning party's change in vote and the second party's change in vote. In the case where two main parties contest a constituency, if the winner has a vote rise of 5%, and the loser has a loss of 4% (with the rest disappearing off to the marginal parties), then the difference is 9%, and the swing is 4.5%. This is a reasonably meaningful measure, giving some indication of the proportion of voters deserting one party for the other.

But what we have here is not a two party fight, but more a three party one. Both first and second place parties increased their vote. So although the calculation is (5.5% - 3.1%)/2, giving that 1.2%, the implication of the calculated swing that 1.2% of voters deserted the LDs for the Tories is quite blatantly false.