[Election-Methods] STV in the context of modeling voters

Jonathan Lundell jlundell at pobox.com
Sun Dec 30 10:55:18 PST 2007

On Dec 30, 2007, at 2:14 AM, Dan Bishop wrote:

> In the coming weeks/months/whenever-I-feel-like-it, I will be  
> performing
> simulations to evaluate the performance of multi-winner methods.  In
> order to do this, I will make the assumptions that:
> * There is a uniform linear political spectrum.  (Other models of  
> voter
> behavior will be considered later.)
> * Candidates are uniformly-distributed random variables in.
> * All votes are sincere.  (i.e., a voter at position V votes A>B iff
> abs(A-V) < abs(B-V))
> The last two assumptions, that no strategy is involved in either
> nominations or voting, is admittedly unrealistic.  But, as I see it,  
> in
> order to know the best strategy to use with a method, you must first
> know how it would behave without strategy, so that's a useful thing to
> analyze.

The first assumption is pretty unrealistic as well. I look forward to  
seeing your other voter models.

For example, I was thinking of the problem faced by US Democratic  
primary voters during the current cycle. Granted, they don't have to  
rank the candidates (except in Iowa, where there's a limited  
contingency process), but they still have to come up with a first  

Looking at the candidates, though, it seems to me not terribly useful  
to try to order them in any one dimension, and to the extent that they  
can be ordered on multiple dimensions, very difficult to resolve those  
rankings in to a single ordering (or a first choice).

Many voters appear to value "electability", for example. But we're  
faced with the difficulty not only of trying to rank (and perhaps  
weight) electability, but then to figure out how that weighting  
figures into some larger process that looks at how effective the  
candidate might be if elected, how we feel about their stands on  
various issues (Iraq, health care, etc). Then there are second-  
(third-?) order considerations. I may think that Iraq is a more  
important issue than health care, but question the extent to which any  
particular candidate, however much I might identify with their  
position, can do about it. So maybe I should weight health care plans  
more heavily, if I think that we're "ready" for serious reform.

And so on.

I tentatively conclude that it's not very helpful to model that kind  
of decision process, partly because it's impossibly difficult to model  
and, more important, to validate the model.

And here's where Gilmour's 'contingency' becomes especially relevant.  
Voters aren't dispassionate computers with elaborate linear  
programming built in. What they *can* do (we know because they  
actually *do* it) is to decide, finally, on their first choice. And  
having accepted that, it's no great leap to assume that they can  
decide on a second choice contingent on the unavailability, for  
whatever reason, of their first choice.

I'll try not to turn this into a pitch for STV, but it strikes me that  
one of its attractions may be that with its explicit reliance on  
contingent choices, it asks voters to solve a problem they're prepared  
to deal with, without solving impossible resolutions of conflicting-- 
and vague--personal value scales.

As a voter, I prefer to think in terms of contingent choices. I don't  
*want* to solve the strategy problem presented by approval voting.  
With range voting, I don't feel that I'm in a position to assign  
cardinal weightings to the candidates (never mind for the moment how  
they're ultimately counted), nor do I want to be burdened with then  
turning those numbers into a strategic game to maximize my outcome.

Sure, STV is manipulable. But so is everything else. And its implicit  
decision model conforms to something that I, as a voter, can make  
sense of. And in making my contingent choices, STV's later-no-harm  
property becomes important to me. Of course I'd like it to be  
monotonic, etc, but on *my* value scale, its advantages, in practice,  
outweigh its shortcomings--in practice.

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