Saturday, May 10, 2008

How the London Assembly could have been so different

Amidst all the euphoria or sorrow about the results of the GLA elections there's been comparatively little number crunching about the Assembly results. And one area has not been given much light at all - the potential for large parties to game the system to maximise their advantage. And the results are surprising.

The Assembly is elected by the Additional Member System, another name for Mixed member proportional representation and I can no better than recommend the Wikipedia article for details. But also take a look at Overhang seat for details on how the system can produce disproportionate results if a party wins far more constituency seats than its list vote "entitles" it to.

Since a party's success in a constituency cancels out its entitlement on the list, one can legitimately wonder what would happen if a party was able to uncouple its constituency and list results and run as two nominally separate parties that will act as one in the assembly chamber. When Italy used this system major parties on both the right and left set-up decoy lists with the result that they both gained far more seats than the implementers of the system expected. (For the London Assembly it may not be necessary to have a strict "decoy list" itself as constituency candidates do not have to be attached to lists.)

In the interests of fairness I've done the calculations three times, looking at the effect of each party then both running decoys. And the results make for interesting consideration.

As elected the Assembly had the following result:

11 Conservatives (8 constituencies, 3 list)
8 Labour (6 constituencies, 2 list)
3 Lib Dems
2 Green

Now if the Conservatives had run a decoy then the results of the assembly would be as follows:

15 Conservatives (8 constituencies, 7 list)
6 Labour (all constituencies)
2 Lib Dems
1 Green

The main effect would be that the Conservatives would have a majority in the Assembly, whilst Labour would not have a single list member and thus have no representation at all for much of London. Both the Lib Dems and Greens would lose a member, with the latter also losing recognised party status and thus their entitlement to group support funding. (I don't know if the Assembly rules would allow them to form a "technical grouping" with the BNP to qualify for funding but since that's realistically not going to happen let's not speculate.)

But what if instead Labour tried a decoy? We get:

8 Conservatives (all constituencies)
12 Labour (6 constituencies, 6 list)
2 Lib Dems
2 Green

This time round the Conservatives are left without any list representation. Labour are now one seat short of a majority and if Labour, Lib Dems, the Greens and the BNP all combined together (as they already did at the first Assembly meeting) then they would have a 2/3 majority to block the Mayor's proposed budget.

And if both parties tried decoys? The result would be:

13 Conservatives (8 constituencies, 5 list)
10 Labour (6 constituencies, 4 list)
1 Lib Dem
1 Green

Yes the BNP would be off the Assembly. Both the Lib Dems and the Greens would be down to a single member without recognised party status, and it would be interesting to see if they could put aside their rivalry to form a technical grouping to share party funding. (I don't know if this is technically possible.) Meanwhile there would be a Conservative majority in the Assembly.

Now will anyone else pick up on this and consider trying this tactic? Something similar was attempted by Forward Wales at the last Assembly election who ran all their candidates as independents, but the votes just weren't there for them. How long before the major parties try it? Or will the system get abolished before then?


Anonymous said...


I like your number-crunching ways, eventhough we differ on what is important for a good voting systems and for encouraging people to vote. I thought you might be interested in this analysis of the London elections - inc plenty of stats on how the different voting systems worked.

Anonymous said...

Ah. I see my link hasn't worked. You can get the report via the Make Votes Count site or


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