# The Davison Run-off

New Democracy donald at mich.com
Thu Dec 26 06:45:32 PST 1996

```Dear members of this list,

I would like to announce a change I am thinking about making to the
Instant Run-off method. The change has to do with the candidate that is to
be dropped first. As you know, Instant Run-off drops the candidate with the
lowest vote total on the first set of selections. I am going to drop the
candidate first that has the most selections in the last set of selections.
The sooner a candidate gets selections the less likely he will be dropped
first. This method favors the candidates that receive the most favor from
the voters.

Sometimes this candidate dropped from the last set of selections will
be the same candidate that would have been dropped by Instant Run-off - and
other times it will be a different candidate.
Sometimes the winning candidate will be the same candidate that would
have won with Instant Run-off - and other times it will be a different
candidate - sometime it will be the same winner as by Condorcet.

An example will show how this may give us different results. The example
below is an example that Steve put in a reply to one of my posts.

Steve's first example:  35 ABC   16 BAC    16 BCA    33 CBA

The winner of the last set of selections is candidate C.
Therefore C is dropped - giving us the following new selections.

New selections:   35 AB    16 BA     16 BA     33 BA

We have a majority winner - which is candidate B.

Let us consider another example by Steve:

Steve's second example: 46 AB    20 B     34 CB

In this example we must fill in the missing selections. We have the right
to do this because if a voter does not fill in a selection that is the same
as saying he does not care which is last - any of the remaining can be
last. In  the two cases above in which there is no third selection we can
assume the third to be the only possible choice remaining. In the one case
in which two selections are left off, we can assume that the voters do not
care which is second or third. I am going to divide the second and third
spots between A anc C.

Therefore I am writing Steve's second example as follows:

46 ABC    10 BAC     10 BCA     34 CBA

The winner of the last set of selections is candidate C.
Therefore C is dropped, giving us a new set of selections.

46 AB     10 BA      10 BA      34 BA

We have a majority winner, which is candidate B with 54B.

Another example:

499 ACB       B wins third selection set with 502
498 BCA       B is dropped
3 CAB       C wins

This following example already has a majority winner but I include it to
show that this new run-off feature will confirm a majority winner.

501 ACB       B wins third selection set with 502
498 BCA       B is dropped
1 CAB       A wins

In the case of more than three candidates I would initially say that
the winner of the last set of selections be dropped first as I did in the
above examples. This would produce some changes in the other selections -
causing a new sets of selections. The winner of the last set of selections
of these new selections would now be dropped - etc - until we have a winner
with a majority.

Condorcet people have often said that it is not proper for Instant
Run-off to drop the last candidate. The solution is simple - we do not drop
the last - we drop the candidate that is the lead candidate in the last set
of selections.

If this run-off change pans out I will call it the "Davison Run-off"
and incorporate it into my list of election reforms - and Steve can have
the name Instant Run-off for Condorcet.

I hope everyone had a good holiday - I "ate crow" for my holiday dinner.

Donald of New Democracy at http://www.mich.com/~donald

```

More information about the Election-Methods mailing list