[EM] Simulation of Duverger's Law

[Kevin Venzke]

Hi Greg,

--- En date de : Jeu 16.10.08, Greg Nisbet <gregory.nisbet at gmail.com> a écrit :
> Complete non-sequitur but still a point I don't
> entirely understand:
> IRV, FPTP and Contingent Vote all lead to two party
> domination according to
> Duverger's law.

I don't think Duverger's law suggests this regarding IRV.

I think what we need to see, are IRV elections to a chamber that is
not parliamentary (i.e. there is no particular prize for one party getting
the most seats). Perhaps in that situation IRV could support more than
two parties.

> Why doesn't France's Two Round System lead to the
> same result? Pretend you
> have a ballot consisting of rank ordering and a separate
> FPTP checkbox,
> would this similarly avoid two party domination?

No, the "second chance" nature of the two rounds is essential to altering
the incentives so that there is not so much at stake in the first round.
There is always at least some choice the voters can still make, in the
second round.

But this means more candidates can be nominated. And that means that it
may be somewhat arbitrary which candidates end up as the finalists.

Kevin Venzke