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

Raph Frank raphfrk at gmail.com
Tue Jul 10 02:23:46 PDT 2012

On Sat, Jul 7, 2012 at 5:10 AM, Michael Ossipoff <email9648742 at gmail.com>wrote:

> Raph:
> Looking again at your Sainte-Lague splitting-strategy example, I don't
> think that the situation is quite as bad as you said.
> The smaller group, with 39% of the voters ends up with only 53% of the
> seats, unless I've made an error, which is quite possible.

I think you are correct.  The "bonus" only happens for the first seat that
each party gets, so they can only get one each (26 total) before the rest
go back to the large party, so 26 out of 49, 53% as you said.

It might be possible to tweak it by having more micro-parties, but the more
accurate it needs to be, the harder for it to happen in practice.  It was
really just illustrating the point that Sainte-Lague could favour very
small parties.

Even just using 0.7 as the first divisor instead of 0.5 might eliminate it
in practice, but that is bias against smaller parties which has the same
effect as d'Hondt, giving voters an incentive to vote for larger parties.

> 2. d'Hondt can strategically force people to vote for a compromise party
> instead of their favorite, in order to maximize their weight in parliament.
> What other solutions are there? Largest-Remainder. In your example, In LR,
> the large party immediately gets 29 quota seats, and then the first
> remainder seat. The small parties get the rest of the remainder seats.

Another possibility is Largest-Remainder, but with STV transfers allowed.
The ranking could even be set by the parties.  This would mean no lost
votes, but still be very simple (voters just pick one party).

Even national level pure STV, but by party, would be possible.  There would
be no "elected" party.   In each round the party with the lowest remainder
would be "eliminated" and have its number of seats "locked" by rounding
down.  There could then be surplus transfers.

I think a transfer system of some kind would make people much more
confident to vote for their favourite party.  Even if on average the system
is unbiased, voters wouldn't want to risk giving a majority to a different
group.  Transfers would more consistently give a majority of the seats to a
majority of the voters (assuming it is a solid coalition).
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