[EM] IRV vs Plurality

[Dave Ketchum]

On Jan 13, 2010, at 4:49 AM, Juho wrote:
> On Jan 13, 2010, at 9:14 AM, robert bristow-johnson wrote:
>
>> it still is a curiosity to me how, historically, some leaders and  
>> proponents of election reform thunked up the idea to have a ranked- 
>> order ballot and then took that good idea and married it to the IRV  
>> protocol.  with the 200 year old Condorcet idea in existence, why  
>> would they do that?
>
> 1) The basic idea of IRV is in some sense natural. It is like a  
> street fight. The weakest players are regularly kicked out and they  
> must give up. I'm not saying that this would lead to good results  
> but at least this game is understandable to most people. Condorcet  
> on the other hand is more like a mathematical equation, and the  
> details of the most complex Condorcet variants may be too much for  
> most voters. Here I'm not saying that each voter (and not even each  
> legislator) should understand all the details of their voting  
> system. The basic Condorcet winner rule is however a simple enough  
> principle to be explained to all. But it may be that IRV is easier  
> to market (to the legislators and voters) from this point of view.

When there is a CW in Condorcet, the CW has won in comparison with  
each other candidate.  While a few may like X or Z enough better to  
have given such top ranking, the fact that all the voters together  
prefer the CW over each other should count, and does with Condorcet.

Else there is a cycle in Condorcet.  Perhaps the following Minimum  
Margins Method Condorcet variant should be used to establish  
Condorcet's preferability over other methods.  Then let other variants  
compete with this one before finally deciding which to use.

Minimum Margins Method:  Consider the cycle, such as A>B>C>A, and the  
margins that create it, such as 60A>30B, 40B>20C, 21C>20A.  Delete the  
weakest margins as many times as needed to destroy the cycle - in this  
case A becoming the CW (note that if one C>A voter had voted A>C in   
this election, A would have become CW with no cycle).
>
> 2) IRV is easier to count manually. Condorcet gets quite tedious to  
> count manually when the number of candidates and voters goes up. One  
> can use some tricks and shortcuts to speed up manual Condorcet  
> counting but IRV probably still beats it from this point of view.  
> Manual counting was the only way to count for a long time. Nowadays  
> we have computers and Condorcet tabulation should thus be no problem  
> at all (at least in places where computers are available). But this  
> is one reason why IRV has taken an early lead.

When an election district has only one polling place, life is simple.

When the district is a state or city, life is more complex for each  
method.
      With IRV you first want top ranks from all the ballots in the  
district.  If there is no majority winner all the ballots for the  
worst loser must be scanned for all the polling places for whom those  
voters ranked next.  Repeat until winner gets decided.
      With Condorcet each ballot gets scanned one time and its content  
added into an N*N array, with such arrays summed for the whole district.
>
> 3) Large parties are typically in a key role when electoral reforms  
> are made. Election method experts within those parties may well have  
> found out that IRV tends to favour large parties. In addition to  
> trying to improve the society the best way they can, political  
> parties and people within them also tend to think that they are the  
> ones who are right and therefore the society would benefit of just  
> them being in power and getting more votes and more seats. The  
> parties and their representatives may also have other more selfish  
> drivers behind their interest to grab as large share of the power as  
> possible :-). IRV thus seems to maintain the power of the current  
> strongest players better than Condorcet does, and that may mean some  
> bias towards IRV.
>
> 4) The problems of different election methods may appear only later.  
> A superficial understanding of IRV reveals first its positive  
> features. Like in Burlington the negative features may be understood  
> only after something negative happens in real elections. This  
> applies also to Condorcet. On that side one may however live in the  
> hope that the problems are rare enough and not easy to take  
> advantage of so that sincere voting and good results would be  
> dominant. The point is that IRV may be taken into use first (see  
> other points above and below) without understanding what problems  
> might emerge later. And once it has been taken into use it may well  
> stay in use for a long time (electoral reforms are not made every  
> year, people have already gotten used to the method, having to  
> change the method could be seen by the society/legislators as a  
> failure/embarrassment, and people/parties who were elected based on  
> those rules and are strong in that system may be reluctant to change  
> the rules).
>
> 5) Both IRV and Condorcet have some weak spots that can be attacked.  
> As you point out the weak spots of IRV may well be worse than those  
> of Condorcet methods (for most typical use cases in politics).  
> Different problems may have different weight in different political  
> environments. For example in countries with strong two-party  
> tradition and single party government some Condorcet properties like  
> the possibility of electing candidates that do not have strong first  
> preference support in the ballots may work against it (both in the  
> case that one does not want the system to change and in the case  
> that one wants to renew the system). Also strategic voting and fraud  
> related problems (like later no harm, burial, precinct counting) may  
> be seen in different light in different societies, e.g. in countries  
> where strategic voting is the norm vs. in ones where sincere voting  
> is the norm. One may thus have/develop points of view where  
> Condorcet looks worse than IRV (I guess it could also be worse for  
> some uses in some societies from some points of view).

So some whose backers tend to rank them top object when they lose  
because more other voters rank them below others?  I like better  
Condorcet's having A win over B when more voters prefer A>B to B>A  
without caring which is top ranked by more.

single party government?  If some voters rank B>A and some rank C>A, A  
still wins if the total is A>B and A>C.  Good to get vote counts that  
identify what A is seen as doing well, and what it had better improve.
>
> Juho
>
> P.S. One more reason is that Condorcet promoters seem to be lazier  
> that IRV promoters :-). Condorcet has made some progress in the  
> academic circles but not yet in politics.

Agreed, though this is not a reason why IRV deserves to win this race.

Dave Ketchum