[EM] STV+AV

[Raph Frank]

On Sat, Feb 4, 2012 at 8:07 PM, Bryan Mills <bmills at alumni.cmu.edu> wrote:
> Now, despite a 50/50 natural split, the rural party has a 60% supermajority.
>  And, of course, if you draw the district lines differently you can do the
> same thing for the urban party.

This was attempted in Ireland, look up Tullymander.

They created 4 seat districts where the governing parties had a slight
minority (so the split would be 2-2) and 3 seat ones where they had a
slight majority (so the split would be 2-1)

It blew up in their face, and they lost by a landslide (may of the 4
seaters went 3-1 against them).

You are assuming that there is a very narrow band of support for the
parties.  It is unlikely to be that stable in practice.  Even a 5-10%
swing would be enough to break the assumptions.

In the Tullymander case, a 4 seater with 55% - 45% only needs 5% to
swing to a 3-1 disaster, and similarly in a 3 seater, a 55% - 45% only
needs 5% change to change which part gets the final seat.

> So there's still relatively little hope that a system with such small
> districts would produce a party-proportional legislature.  As you point out
> elsewhere, it might still be possible to get an ideologically-proportional
> legislature if you can get the parties themselves to shift ideologies.

Another issue is that a seat might be party safe, but not politician
safe.  Your party might be guaranteed 2 seats, but not you.
Politicians would need to keep the locals happy (this has pluses and
minuses).

A party can decide only to run 2 candidates in 5 seaters, but then
they give up getting a majority.

> They do maintain the constituent-legislator relationship, *for the subset of
> voters who voted in favor of the legislator*.  For the remaining Droop quota
> of un- or under-represented constituents the nonexistence of the
> constituent-legislator relationship is also maintained.

However, that is smaller, down from up to 50% to up to 1/(seats + 1)
of the voters.