[EM] SODA strategy

[Juho Laatu]

I checked the definition of SODA at the wiki page. Since the method consists of multiple phases and has many rules, it was difficult to find a simple mapping from that to one simple claim that could be proved or falsified. I also had some problems with terms semi-honest, non-semi-honest, self-reinforcing and defensive strategy below.

I had multiple thoughts on where SODA might be vulnerable and where not, but on the other hand I didn't know which phases were supposed to be "strategy free" and which way (the phases whose role I wondered were nomination, preference order declaration, voting and vote transfer). Maybe one could do this in smaller pieces, like handling separately the chicken problem for one of the phases etc. Another approach would be simply to list all identified possible vulnerabilities and then prove that all those cases are harmless. Is there one major claim that could sum it all (at least the claims) in one sentence or should we start from smaller pieces?

Juho


On 9.8.2011, at 16.14, Jameson Quinn wrote:

> SODA is not strategy free. Even if you make the assumption that candidate preferences are honest because dishonesty will be detected and punished by voters -- an assumption which puts the system beyond the reach of the Gibbard-Satterthwaite proof -- the fact remains that you can construct strategic scenarios.
> 
> However, it seems to me that SODA is not just a less-strategic system than most others, but radically so. Unlike Approval, semi-honest approval strategy is not something voters must deal with at least implicitly. But like approval, non-semi-honest strategy is relegated to a tiny minority of voters in a tiny minority of cases. The system can deal with all the commonly-discussed strategic problems, including chicken, center squeeze, and honest cycle. I honestly suspect that strategy under SODA would be favored less than half as often as any other good deterministic system I know of, including Approval, Asset, Condorcet (various), IRV, Median, and Range.
> 
> So, how would you set out to make this idea demonstrable or falsifiable? What rigorous statement about strategy and SODA could I make that would be testable, preferably using simulated elections or mathematical demonstration/counterexamples? What voter model could capture enough of the sophisticated strategic thinking of which humans are capable?
> 
> How about "SODA requires no self-reinforcing or defensive strategy"?
> 
> These are honest, not rhetorical questions. I appreciate good responses, good research questions, from anyone, whatever you expect that the results of that research would be.
> 
> Thanks,
> JQ
> ----
> Election-Methods mailing list - see http://electorama.com/em for list info