D. Batch Elimination of Candidates

One could eliminate candidates in batches rather than one by one. There are two rationales for this. The first is practicality. If there are many candidates, each with very few votes, then it would be tedious to eliminate them one by one. The second is efficiency. If it is known that several candidates can't win, then it makes sense to eliminate them all right away.

The first method is to eliminate all candidates who have fewer votes than a flat cutoff. This would take place immediately after all surplus votes have been transferred to allow all candidates to take advantage of surplus votes to avoid being eliminated in this fashion. This will be useful when there are many candidates with very few (or even no) first place votes. With many such candidates, it would take many rounds to eliminate them one by one. The batch elimination simplifies the count by eliminating all candidates with very few votes in one round. Note that this will possibly eliminate candidates who have a chance of winning. However, this is not a problem as long as the cutoff is chosen wisely.

The second method is the same as the first, except that the cutoff is chosen as a percentage, say 0.5%, of the total number of votes cast. This method is suggested in the STV rules in Behind the Ballot Box.

The third method is to eliminate all candidates immediately who have no chance of winning. This can happen before surplus votes are transferred and at any time throughout the count. To test if a given candidate can win, it is assumed that she will receive all surplus votes and all transfers from eliminated candidates. Under this assumption, a candidate can win if it is possible that she can beat all candidates between her and the last seat. If it is known that a candidate can't win then she should be eliminated immediately. It is possible that at a given round, that several candidates can't possibly win and they should all be eliminated in a batch.