Single Transferable Vote is a voting system for electing members to legislative bodies. It is one form of proportional representation. Even though it is a very old system, it is not well-known in the United States. Law Professor Steve Mulroy, a proponent of the system, has this clear explanation at ElectionLawBlog.
https://en.wikipedia.org/wiki/Single_transferable_vote
See US regimes using STV.
This “clear explanation” does contain one factual error, of the sort that sows confusion in the long run. Mulroy says that to fill one of 5 seats you need 1/5 of the vote. Actually, you need one more than 1/4 of the vote. One way to understand this intuitively is to ask how many votes you need to fill one seat (what we usually call IRV). The answer is not 1/1 of the vote, which would be all votes. The answer is one more than 1/2 of the vote. Just generalize that to more than one seat.
It’s either 1/5 or 1/6 of the vote depending upon which quota system you use…. either the Hare Quota or the Droop Quota respectively. It’s either 1/n or 1/n+1. No system uses 1/n-1. n = number of seats to be filled.
@Bob
Take the following example:
Filling 4 seats; 100 votes – Using your (1/(n-1))+1 formula you get 34 votes per seat:
Cand A = 33
Cand B = 32
Cand C = 25
Cand D = 7
Cand E = 5
Nobody got the quota, so we eliminate Cand E. Say all of those go to Cand D… new totals:
Cand A = 33
Cand B = 32
Cand C = 25
Cand D = 12
Still nobody hit the quota, but we have the exact number of candidates left as seats to be filled. This could work, but this isn’t single transferable… this is a weird hybrid of Instant Run-Off and Single Non-Transferable. You’d really only ever drop the lowest polling candidates, and never transfer surplus votes. Single Transferable MANDATES that nobody get a seat without hitting the quota except for the absolute last seat (called the largest remainder).
Correction to my last post Cand E should have 3 votes in the first round and Cand D 10 in the second round. That doesn’t change the problem of having no one hit the quota though.
Andrew, do you know of a jurisdiction that uses STV with a Hare quota in public elections?
And, are you arguing that the Hare quota prevents anomalies like the one you describe with the Droop quota? In practice, this kind of anomaly is vanishingly rare except with very small electorates (e.g. 100 voters).
https://en.wikipedia.org/wiki/Comparison_of_the_Hare_and_Droop_quotas
—
PR — RATIO = Total Votes / Total Members [odd, 3 or more]
Surplus votes down. Loser votes up.
—-
Exact – Voting power of a Member = Votes gotten
If a party gets 43% of the popular vote they should get 43% of the political power. Mulroy’s system does not achieve this. It also does not provide geographical proportionality if the areas have different numbers of voters.
A better system:
(1) Divide California into 848 electoral areas of roughly 15,000 voters each based on 2018 election. These 848 electoral areas will be combined into 120 districts of approximately equal electorates.
(2) Voters will rank candidates in their electoral area by STV. Statewide quota will be 3000. If a voter does not express full preferences, the voter will use his first preferences rankings for any remaining preferences.
Example: George ranks his preferences: George, John, Tom, James, Jim, JQ, Andy. A vote who ranks George, Andy, James; will be assumed to then rank John, Tom, Jim, and JQ. This assures no exhausted ballots without requiring each voter to personally express them.
Surpluses in excess of 1-1/2 quotas will be distributed, candidates with fewer than 1/2 quota will be eliminated in turn. Transfers may be made to elected candidates, using the New Zealand method.
On completion each elected member will represent between 1500 and 4500 voters. Thus an area where 18,000 votes were cast will nominally elect 6 members, but may have more or less depending on their relative voting weight.
The members in each district will elect a representative to the 120-member unicameral assembly in Sacramento, where they will execute day to day legislation. The full membership of around 4000 members will vote on final passage. They will also choose the executive officers of the state.
Having party HACKS pick exec/judic officers is automatic PARTISAN law enforcement.
See SCOTUS HACKS for example.
—
PR and NONPARTISAN AppV.
The commentaries are correct. In my book, our use the threshold of exclusion of 1/ n + 1. In the example of selling five seats, that would be one vote more than 1/6 of the total vote. In a very condensed blog post, I simplified by saying that anyone with at least 1/5 would get a seat, which is true, and intuitive since we’re focused on PR, but I realize now misleading. I’ll correct it. Thanks
Droop quota wastes about 100 percent / (N+1) of the votes
Elect 3 – small legislative body – 1,000 votes
251 elected
251 elected
251 elected
247 wasted = 24.7 percent
Less wasted with larger number to be elected
— BUT still may be the real *marginal* difference between majority and minority rule
— esp in larger bodies — eg 0 to 5 percent margins.
—
PR and AppV