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The Nitty Gritty on Ranked Choice/Single Transferable Voting

Nitty Gritty

Tomorrow Santa Clara voters will be asked to decide whether the City should adopt a two-district, at-large Council seat system and a Ranked Choice, Single Transferrable Vote (RCV/STV) election method. The system is used in Ireland, Australia, New Zealand, Malta, Cambridge MA and Minneapolis MN, and some elections in India, Nepal and Pakistan.

Yet voters won’t even find the words “Single Transferrable Vote” on the ballot. Nor will they find it on the website of the PAC that is promoting this, Better Elections For Santa Clara.

In order to make an informed decision about this, voters need to understand that what is being proposed is not the more familiar San Francisco-style instant runoff. STV is an at-large proportional representation method that reduces the percentage needed to win in order to boost the representation of minority groups and views.


RCV/STV involves ranking candidates, on a list, from most desirable to least desirable—identical to the voting method for instant-runoff systems. However, in instant runoff low vote-getting candidates are eliminated and those ballots’ second (and third) choices are counted until one candidate passes 50 percent.

In an STV system the percentage needed to win—called the Quota—is calculated based on the number of offices to be filled, and results are calculated through a process of redistributing votes in several rounds, based on the voters’ rankings. To achieve the proportional representation, elections must be at-large for multiple seats.

If candidates surpass the Quota their surplus votes are redistributed to the ballots’ second choices. If no candidate achieves the Quota, the last-place candidate is eliminated and those votes are transferred to the ballots’ second choices. This transfer can be whole or fractional votes.

There are about half a dozen methods for calculating the Quota, and a similar number of vote counting and transfer methods—some of which use statistical methods and fractional votes.

The Droop Quota is the most commonly used method for counting votes in an STV system. First, the total votes cast in an election is divided by the number of available vacancies for the position, plus one. Then, one is added to the quotient. For example, if 115 votes are cast in an election for three seats, the quota is calculated as follows:

(115 votes cast/(3 vacancies  + 1)) + 1 = (115/4) + 1 = 29.75 votes needed for election

 The first round of STV vote counting is straightforward: the first preference on each ballot is a vote for that candidate. The votes are tallied and candidates with at least the minimum number of votes required by the Quota, win. In the example candidates with 29.75 votes or more win.

Subsequent STV counting rounds are vote transfers. Surplus votes are the first choice to be transferred; but if no candidate surpasses the Quota, the candidate with the fewest votes is eliminated and those votes get transferred. In last place ties, a candidate is randomly selected for elimination.

No matter whether the votes are coming from an eliminated candidate or from surplus votes from a candidate above the Quota, the transferring process is the same: votes on the transferred ballots go to the next highest-ranked candidate. However, there’s a difference between transferring surplus votes and transferring votes from eliminated candidates.

When candidates are eliminated, all of their votes are redistributed. But when a candidate wins only surplus votes are transferred. So depending on which votes are considered “surplus,” election outcomes can change. To solve this problem, votes are transferred by fractions, keeping the relative distribution the same.

Following the example above, (115 votes cast), one candidate receives 41 votes. That candidate has just over 11 surplus votes to be distributed: 41 – 29.75 = 11.25. The surplus votes get transferred at 11.25/41, or 27 percent of the total. This allows for exactly 11.07 total votes to be transferred. Transferring votes and eliminating candidates continues until there are enough winners to fill the positions.

The Meek system, developed by Brian Meek (1934-1997), is an iterative vote tallying method for STV systems, but it requires a computer and can’t be done manually. Meek allows candidates reaching the Quota to count surplus votes, and transfers those votes throughout the counting based on dynamic weighting. Because it tallies all the votes, Meek is considered preferable to other systems, which can change the results of the election depending on the order votes are counted.

Each candidate is assigned a “keep factor” identifying the percentage of each can keep per round of counting. Candidates under the Quota have a “keep factor” of 1, because they will keep the entire portion of their votes to attempt to reach the Quota. Candidates above the Quota will have a “keep factor” of less than one because their votes will always have a portion transferred to keep them at Quota. This allows candidates to always receive votes intended for them, even if they surpass the Quota.

In the Meek system, the Quota changes when a vote is “exhausted” — when a ballot has no next most-preferred candidate to transfer votes to. Once the ranked candidates are eliminated, the ballot is eliminated. This affects the Quota because the total number of votes cast decreases.

In Meek’s STV system, all the votes are recounted for each counting cycle. So when a candidate is eliminated, the votes are counted as if the candidate was never in the election in the first place. With other STV methods, an eliminated candidate can change the outcome of the election.

This vote tabulation system is complex and raises several questions.

First, will the County Registrar of Voters — the agency that runs Santa Clara’s elections — cannot accommodate ranked choice voting and STV at this time, so tomorrow residents will be voting for a two-district simple plurality at-large system — the system that both federal and state voting rights laws are directed at because of its discriminatory effects.

Second, the proposed charter amendment leaves decisions about vote counting and tabulation to the City Council. The Council has given its endorsement to this change by voting to put it on the June ballot but they have said nothing about how they will decide on the vote counting method. Based on past history, it may be to a Council-appointed committee.


  1. Ed 6 years ago

    Thisexplaination of voting is vs. the normal voiting system, which is “whoever gets the most votes wins”.
    So a 6 word explaination on a voting system vs. an over 700 word explaination.
    The choice is clear. KEEP VOTING SIMPLE. Vote no on A, there is a better way!

  2. TheGoodShipSantaClara 6 years ago

    So this STV is not IRV!. I’m glad Measure A failed and I feel bamboozled by this description of how STV works not being included in any ballot information. Really shakes my faith in this Council that with this lawsuit pending to go against them they put this dog on the ballot. How much did the City spend on Measure A? It didn’t come out of the pockets of our incumbents on Council clearly.

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