[EM] Voting Systems Study of the League of Women Voters of Minnesota

[Markus Schulze]

Hallo,

I just read the Voting Systems Study of the League of
Women Voters of Minnesota (2544 kB):
http://www.lwvmn.org/LWVMNAlternativeVotingStudyReport.pdf

The committee is in favor of IRV. In the summary, they
write:

> Condorcet Voting System (Voters rank candidates; winner
> is the one who can top each of others in a series of
> head-to-head contests)
> * Allows voters to express preferences among candidates
> * Considered by some mathematicians to best identify
>   winner in three-way race
> * May result in a tie that requires pre-election decision
>   on how to break tie
> * Is vulnerable to manipulation
> * May be difficult for voters to understand
>
> Instant Runoff Voting System (Voters rank candidates;
> votes for candidate with fewest firstchoice votes are
> redistributed according to their second choices until
> one candidate achieves a majority)
> * Ensures majority rule
> * Allows voters to express preferences among candidates
> * Eliminates problems of spoiler candidates knocking off
>   major candidates
> * Eliminates need for run-off elections
> * Does not meet mathematical requirement for monotonicity

In short: IRV violates monotonicity, but it ensures majority
rule and eliminates the need for run-off elections and it is
spoiler-proof and immune to manipulation.

Furthermore, in appendix 3 they argue that Condorcet requires
a change of the constitution while IRV doesn't.

Markus Schulze