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March 7, 2006
Annual City Meeting Election Results
Manually verifying the Burlington IRV
tally
Burlington's Accu-Vote voting equipment produces a series of files
containing an
anonymous record of each voter's rankings. The City then uses
software called Choice Plus Pro to perform the
IRV tally on those rankings. To manually verify that the software
is correctly performing the IRV tally, use the following procedures:
- Copy and paste the candidate names and codes from the input file
(a text file containing such basic information about the particular
election) into your spreadsheet.
- Copy and paste all the ballot images (the records of all ballots
cast) from the PRM files into column A of your spreadsheet below the
candidates names and codes. The actual PRM files from the March
7, 2006 election are here
(zip file).
This should give you thousands of rows
of data that look like this:
000001-00-0003,10000,001,1)
C06[1],WI01[2],C01[3],C02[4],C03[5],C04[6]
000001-00-0004,10000,001,1)
WI01[1],C01[2],C02[3],C03[4],C04[5],C05[6]
000001-00-0005,10000,001,1) C01[1],C02[2],C03[3]
000001-00-0006,10000,001,1) C02[1],C03[2],C04[3]
000001-00-0007,10000,001,1) C03[1],C04[2],C05[3]
Each line of text represents a separate ballot. The data to the left of
the ) symbol include information about the ward and ballot
number. It can all be ignored for the IRV tally. The candidates
are indicated by number rather than name (e.g. “C03” refers to the
third candidate on the ballot for that office. See the input file for the list of
candidates to which these codes refer). Each line of text in the file
lists the candidates
in the order that one particular voter ranked the candidates on his or
her ballot.
- Convert text to columns using delimited text, choosing commas (,)
and left square brackets ([) as your delimiters. The data
enclosed in square brackets, such as [2], are auditing marks that show
the ranking order that the voter gave to the particular
candidate. For the IRV tally, they can be ignored.
Once you convert the data, delete the columns containing the right
square brackets (]).
- Now the process is to total up the first choices for each
candidate. These will be the first round tallies.
- Then you will eliminate one or more candidates with the fewest
first choices (as explained in steps below), and repeat the process
until there are only two candidates left.
- Sort the ballot images by 1st choice.
- Let’s assume the 1st choices are in column E. You can use a
formula to count the number of 1st choices for each candidate.
Copy those values (not formulas!) into a table that lists all the
candidates and has spaces for multiple rounds.
- Determine which candidate or candidates to eliminate. This will
be the candidate with the fewest votes. Under Burlington rules,
if the sum of votes for the two or more candidates with the fewest
votes is less than the votes for the candidate with the next fewest
votes, you can eliminate the two or more candidates simultaneously.
- When you eliminate a candidate, their votes get transferred to
the voters’ next choices. The easiest way to do this is to select
all the rankings for all the ballots listing the eliminated candidates
and simply cut them and paste them one column to the left. Not
that you may need to resort the data you just move and make sure that
you didn’t transfer votes to an eliminated candidate. If you did,
you’ll need to shift those votes over one or more columns until the
ballot count for a continuing candidate (or there are no more choices
left in which case the ballot is exhausted). If you used formulas
to count first choices, those formulas should automatically give you
2nd round totals. Copy and paste the values of the totals into
the 2nd column in your totals table.
- Sort the data again by 1st choice and repeat process until you’re
left with the top 2 candidates.
- A few details
- Duplicate rankings. If a voter gives the same rank to more
than one candidate, the voting equipment will store that ranking with
an equal sign. For example, a ballot image that looks like this:
000001-00-0004,10000,001,1)
C01=C02=CO3[1],C04[2],C05[3]
means that the voter listed C01, C02 and C03 all as 1st choices, C04 as
a 2nd choice and C05 as a 3rd choice. Under Burlington rules, a
duplicate ranking is skipped if all the
duplicate ranked candidates have been eliminated when it is reached,
counts for one candidate if exactly one of the duplicated ranked
candidates is still in the running, and exhausts if two or more
candidates are still in the running. In this example, the ballot
exhausts because in the 1st round, all candidates are still in the
running.
- If a ballot transfers to an eliminated candidate in a round, it
counts for the candidate ranked next on the ballot who is still in the
race. So if C01 gets eliminated before C02, a ballot this lists
C02, C01 and then C03 will count for C03 when C02 gets eliminated.
- Ties are broken in favor of the candidate with the most votes in
the previous round, but if two or more candidates have the same totals
in the current round and in all previous rounds (if there are any),
then the tie is broken by a random drawing.
- When you are done, your round-by-round totals should exactly
match those published by the city.
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