[EM] SSD and BeatpathWinner

MIKE OSSIPOFF nkklrp at hotmail.com
Tue Nov 25 22:38:01 PST 2003


You said:

When Mike means Schwartz Sequential Dropping (aka Beatpath
Method) with "Condorcet's method"

I reply:

But I didn't say that that's all that I mean by Condorcet's method. There 
are a number of good versions of Condorcet's method. Here are some of them:

Schwartz Sequntial Dropping (SSD)
Cloneproof SSD (CSSD)
Ranked-Pairs (RP)
Plain Condorcet (PC)
Sequential Dropping  (SD)

Cloneproof SSD (CSSD) and BeatpathWinner are equivalent, always giving the 
same outcome.

Strictly speaking, SSD isn't the same as BeatpathWinner. But in  public 
elections, SSD will choose the same as CSSD. SSD is more natually and 
intuitively defined than CSSD, because the SSD count stops when a candidate 
is unbeaten.

I recommend BeatpathWilnner/CSSD for committees, polls, and organizations, 
because of its elegantly brief algorithm and coimputer program, and its 
freedom from the midcount ties that RP can have in committees, where equal 
defeats can occur.

But RP's brief definition (when midcount ties aren't mentioned)  makes it a 
contender for public elections.

I've mentioned all this here before, but once I described SSD and SD to 
someone complertely new to voting systems. She understood and liked SSD. She 
liked SSD considerably better than SD. SD and RP mention cycles in their 
definitions, but SSD doesn't mention cycles. Very likely, innermost unbeaten 
sets are more intuitive and compelling than cycles, for someone new to 
voting systems. And probably are also more compelling and obvious in their 
motivation and justification than beatpaths comparisons.

Mike Ossipoff

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