[EM] Tactical voting under a jury model
Colin Champion
colin.champion at routemaster.app
Sun Mar 6 05:41:36 PST 2022
I wrote in another thread that "under a jury model with tactical voting,
I have some evidence that the best methods are the ones with the worst
reputations: FPTP and IRV and their extensions". Perhaps some people
would like to see the evidence. The following table gives mean valence
losses (so smaller is better) under a jury model with voters attempting
a burial strategy. It has to be viewed in a fixed-width font.
random fptp sptp av sinkhorn borda mj coombs
115.6767 4.2340 15.4462 3.4934 22.3533 21.3425 - 36.3451
condorcet benham btr nanson minimax minisum rp river
schulze asm
- 3.5469 4.6945 9.5228 7.7089 8.0696 8.4014
8.3864 9.6397 9.8513
condorcet+ random fptp sptp av borda
9.9406 4.9425 11.5035 3.5441 14.2516
copeland+ random fptpf fptpr sptp avf avr bordaf
bordar minimaxfminimaxr
11.4423 9.6349 10.7388 12.4150 9.5974 10.5371 14.4200
12.7967 8.7613 12.0312
smith+ random fptpf fptpr sptp avf avr bordaf
bordar minimaxfminimaxrtideman q&dc
9.6397 4.9559 4.9856 11.5026 3.5442 3.5532 14.2516
10.0643 7.7106 7.7106 4.0854 7.3363
AV (=IRV) seems to be best, while most Condorcet methods do badly and
the Borda count does appallingly.
These results are from my own evaluation software; full details are at
https://www.masterlyinactivity.com/condorcet/condorcet.html The call is
"condorcet 5 101 100000 jury:2+bur". Obviously the correctness of my
code is not guaranteed.
I've never seen an evaluation under a jury model, even assuming sincere
voting. I certainly don't rate such models highly, but I think
discussions of voting need a model and spatial models aren't the whole
truth, so it helps to keep alternatives in mind.
CJC
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