[EM] Clone Free Reverse Llull

Forest Simmons fsimmons at pcc.edu
Sat Mar 21 22:03:17 PDT 2020

In a November 14  2009 message Jobst Heitzig gave us "Reverse Llull" a
Condorcet method with nice properties, but subject to crowding. He
challenged us to find a clone free version. Here is one:

1. Well before the election publish a binary tree whose leaves are the
alternatives. Generate this tree with standard cluster analysis software
applied to a questionnaire about the alternatives. Number the nodes of the

2. If there are n nodes, then a ballot is simply a list of the numbers 1
through n. Voters circle the numbers identifying the nodes for which they
prefer the left branch in the published tree diagram.

3. If the number for the root node is circled on more ballots than not,
discard the right branch, else discard the left branch.

4. Apply the method recursively to the remaining branch (if it has more
than one leaf).

That's it basically. Optimal strategy is to circle the node identification
numbers for which you prefer the likely winner of the left branch over the
likely winner of the right. In other words, sincere strategy is optimal.

In the case of fully informed, intelligent voters following this optimal
strategy, the sincere Condorcet Winner will be elected if there is one.
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