2013/5/29 David L Wetzell <wetze...@gmail.com> > Let's agree tentatively that Alternatives to IRV don't really outshine IRV > unless the number of competitive candidates exceeds 4. >
I think that's false (the number should be 2.5), but OK, let's see where you're going with this. Then, if we used a 1+ the output of a poisson dist'n to model the number > of competitive candidates in an election, it could shed some light on the > debate. > > Let's say that since Nate Silver tended to give Obama 2:1 odds over Romney > that we tend to have 1.5 competitive candidates in our current system so a > good starting parameter is 1 + the outcome of a poisson distribution with a > mean of .5. > > Then, > =1-poisson(3, .5, 1)=.002, which would account for how most activists are > non-plussed by the debate over which single-winner election rule is the > best and willing to go with IRV since 1-poisson(1, .5, 1)=.01 and IRV wd > thereby reliably allow the number of candidates who aren't competitive but > able to make a difference to rise considerably. > > But if IRV's use tends to increase the mean number of candidates say to 2 > then 1-poisson(3, 1, 1)=.019, and 1-poisson(1, 1, 1)=.26. Here, it seems > that > that IRV will still suffice most of the time and even when C is larger the > loss from a non-CW candidate winning wouldn't be that bad if (s)he isn't > that far off from the CW candidate. > > But let's say instead we raised the mean to 2.5 then 1-poisson(3, 1.5, > 1)=.066, and 1-poisson(1, 1.5, 1)=.44. We'd still have all the advantages > with none of the down-falls in almost half of the time and in less than 10% > of the time would there be a situation where IRV could be significantly > improved upon. > > But even if the number of competitive candidates did show potential to > balloon, as suggested by simulations and consuitations with experts, then > there'd be scope for switching from IRV to another election rule. But in > the current situation, C tends to be small and it's more important to > improve the quality than the quantity of competitive candidates, which can > be done by expanding significantly the number of non-competitive but > earnest candidates on the ballot and in the public square. > > Also, the bottom line is that when you're advocating for a change in which > single-winner election rule alternative ought to be used, it's not right to > dump the burden of proof on IRV advocates. The amount of time spent > marketing IRV already is a sunk cost and so the burden of proof for > switching ought to lie on the challengers not the defenders of the status > quo progressive electoral alternative to fptp. > As to the burden of proof, I agree with you. In my opinion, that burden has been met. It's still good to avoid infighting, and I'd still vote for IRV out of solidarity, but if I were writing a constitution and I had to choose between, say, IRV and real runoffs, I'd choose the latter in a blink. > > dlw > > ---- > Election-Methods mailing list - see http://electorama.com/em for list info > >
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