<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:times new roman, new york, times, serif;font-size:12pt"><DIV>Greg,</DIV>
<DIV>I generally liked your essay. I rate IRV as the best of the single-winner methods that</DIV>
<DIV>meet Later-no-Harm, and a good method (and a vast improvement on FPP).</DIV>
<DIV> </DIV>
<DIV>But I think you made a couple of technical errors.</DIV>
<DIV> </DIV>
<DIV>"However, because bullet voting can help and never backfire against one's top choice under</DIV>
<DIV>Condorcet, expect every campaign with a shot at winning to encourage its supporters to </DIV>
<DIV>bullet vote. "</DIV>
<DIV><BR>Bullet voting can "backfire against one's top choice under Condorcet" because Condorcet</DIV>
<DIV>methods, unlike IRV, fail Later-no-Help. </DIV>
<DIV> </DIV>
<DIV><A href="http://groups.yahoo.com/group/election-methods-list/files/wood1996.pdf">http://groups.yahoo.com/group/election-methods-list/files/wood1996.pdf</A></DIV>
<DIV> </DIV>
<DIV>In this 1996 Douglas Woodall paper, see "Election 6" and the accompanying discussion on</DIV>
<DIV>page 5/6 of the pdf (labelled on the paper as "Page 13").</DIV>
<DIV> </DIV>
<DIV>Quoting again from your paper:<BR>"As mentioned, every voting system is theoretically vulnerable to strategic manipulation, and IRV </DIV>
<DIV>is no exception. However, under IRV, there is no strategy that can increase the likelihood of </DIV>
<DIV>electing one's first choice beyond the opportunity offered by honest rankings. While there are </DIV>
<DIV>strategies for increasing the chances of less preferred candidates under IRV, like <A id=awum title=push-over href="http://en.wikipedia.org/wiki/Tactical_voting#Push-over"><FONT color=#0000ff>push-over</FONT></A>, </DIV>
<DIV>they are counter-intuitive."<BR></DIV>
<DIV>The Push-over strategy is certainly not limited to improving the chance of electing a "lower </DIV>
<DIV>[than first] choice". Say sincere is:</DIV>
<DIV> </DIV>
<DIV>49: A </DIV>
<DIV>27: B>A</DIV>
<DIV>24: C>B</DIV>
<DIV> </DIV>
<DIV>B is the IRV winner, but if 4-21 (inclusive) of the A voters change to C or C>? then the winner</DIV>
<DIV>changes to A.<BR></DIV>
<DIV>But as you say the strategy isn't "intuitive" , and backfires if too many of the A supporters try it.</DIV>
<DIV>Some IRV opponents claim to like Top-Two Runoff, but that is more vulnerable to Push-over </DIV>
<DIV>than IRV (because the strategists can support their sincere favourite in the second round).</DIV>
<DIV> </DIV>
<DIV>The quite intuitive strategy that IRV is vulnerable to is Compromise, like any other method that</DIV>
<DIV>meets Majority. But voters' incentive to compromise (vote one's front-runner lesser-evil in first</DIV>
<DIV>place to reduce the chance of front-runner greater-evil winning) is generally vastly vastly less</DIV>
<DIV>than it is under FPP.</DIV>
<DIV> </DIV>
<DIV>(There are methods that meet both Majority and Favourite Betrayal, and in them compromisers</DIV>
<DIV>can harmlessly vote their sincere favourites in equal-first place.)<BR></DIV>
<DIV>But some Condorcet advocates are galled by the Compromise incentive that can exist where</DIV>
<DIV>there is a sincere CW who is not also a sincere Mutual Dominant Third winner.<BR><BR>49: A>B</DIV>
<DIV>02: B>A</DIV>
<DIV>22: B</DIV>
<DIV>27: C>B</DIV>
<DIV> </DIV>
<DIV>On these votes B is the CW, but IRV elects A. If the C>B voters change to B then B will be </DIV>
<DIV>the voted majority favourite, so of course IRV like Condorcet methods and FPP will elect B.</DIV>
<DIV> </DIV>
<DIV>Chris Benham</DIV>
<DIV> </DIV>
<DIV><PRE> </PRE><PRE>Greg wrote (Wed.Nov.19, 2008):</PRE><PRE>I have written up my reasons for preferring IRV over Condorcet methods
in an essay, the current draft of which is available here:
<A href="http://www.gregdennis.com/voting/irv_vs_condorcet.html"><FONT color=#0000ff>http://www.gregdennis.com/voting/irv_vs_condorcet.html</FONT></A>
I welcome any comments you have.
Thanks,
Greg
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