[EM] Sainte-Lague vs d'Hondt for party list PR

Raph Frank raphfrk at gmail.com
Mon Jul 2 03:58:42 PDT 2012

Another possibility is "alternative-vote" based PR.

You rank up to 2 parties.  Something like,

Use divisors 2, 3, 5, 7, 9, ...

This is Websters but is d'Hondt-like for the first seat.

The seats would be allocated using that rule, and any party which got no
seats would be "eliminated" and the votes given to the alternative party.

I don't think it matters if you use normal or the modified version of
Webster for the 2nd stage.  This eliminates "micro" parties getting seats
due to the round up from 0.5 to 1.  If 0.5 to 1.0 sized parties get a
boost, then parties would try to aim for those sizes (splitting if needed),
so it breaks the uniform distribution assumption.

For example, 26 parties at 1.5% and one party at 61% for a 49 seat
parliament would split the seats, 20 for the large party and 29 for split
between the micro parties.  The micro parties get 59% of the seats for 39%
of the vote.

This pretty much has the same effect as a threshold, but at least votes can
be reassigned.  You could also have a random threshold.  For example, if
there was 100 seats, then the threshold could be a random number between 1%
and 2% of the vote.  This would make it hard to game the threshold system.

You could also go down the IRV path, and keep eliminating the weakest party
one at a time, until all remaining parties get at least 1 seat.  The ranked
ballot could also have more than 2 slots, but 2 slots is probably enough.
The voters would be recommended to pick a party with > 2-3 seats for their
alternative choice.

Also, has anyone look into picking the number of seats in a range, so as to
minimise bias.  Use Websters, but pick a house size +/- 10 from nominal and
have some measure.  Does that add or remove bias?  That might require a
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