San Francisco 2010 Municipal Election - District 8

The San Francisco 2010 Municipal Election - District 8 took place on 2010-11-02. Scott Wiener won after two runoff rounds, and was also the Condorcet winner.

Runoff Rounds

This diagram shows the votes of each remaining candidate at each round, as well as the breakdown of votes transferred when each candidate was eliminated.

Scott Wiener Rafael Mandelman Rebecca Prozan Bill Hemenger Write-in Exhausted Ballot Scott Wiener Rafael Mandelman Exhausted BallotRound 1Round 2

Pairwise Preferences

For every pair of candidates, this table shows what fraction of voters preferred one to the other. A preference means that either a voter ranks a candidate ahead of the other, or ranks a candidate but does not list the other. Ballots which list neither candidate are not counted towards the percent counts.

Less PreferredMore PreferredScott WienerRafael MandelmanRebecca ProzanBill HemengerWrite-inScott WienerRafael MandelmanRebecca ProzanBill HemengerWrite-in55.4%61.1%88.2%99.5%44.6%53.2%79.6%99.6%38.9%46.8%84.4%99.5%11.8%20.4%15.6%98.0%0.5%0.4%0.5%2.0%

First Alternate

For every pair of candidates, this table shows the fraction of voters who ranked one candidate first ranked the other candidate second.

Second ChoiceFirst ChoiceScott WienerRafael MandelmanRebecca ProzanBill HemengerWrite-inScott WienerRafael MandelmanRebecca ProzanBill HemengerWrite-inExhausted Ballot19.7%45.9%8.7%0.1%25.6%22.2%42.0%2.9%0.3%32.7%42.3%32.0%5.7%0.1%19.9%33.5%11.9%19.1%0.3%35.1%6.7%3.3%3.3%0.0%86.7%

Final-round vote by First vote

For each candidate who was eliminated before the final round, this table shows which final-round candidate the eliminated candidate's first-round ballots went to.

Final Round ChoiceFirst ChoiceRebecca ProzanBill HemengerWrite-inScott WienerRafael MandelmanExhausted Ballot44.8%33.5%21.7%43.9%15.9%40.2%6.7%3.3%90.0%

Honest Approval Set

Another voting system is Approval Voting, which involves indicating one or more candidates you approve of without ranking them. The candidate with the most voters who approve of them wins. It is impossible to know how voters would vote on an approval ballot based on their ranked ballot, but two reasonable assumptions we can narrow down the set of possibe approval ballots. With these possible approval ballots, we can determine which candidates would have had a chance of winning under an approval voting system.

The assumptions we make are:

  • Every voter who ranked at least one candidate would have voted for at least one candidate in an approval vote.
  • Every voter’s approval votes would be consistent with their ranked ballot, that is, they would not vote for a candidate unless they also voted for every candidate who appeared above that candidate on their ranked ballot.

The table below shows the maximum vote margin each candidate could have received (over the next best candidate) in an approval system, subject to these assumptions.

CandidateMost Favorable Scenario
Scott WienerWins 24,843 to 13,617
Rafael MandelmanWins 22,031 to 16,161
Rebecca ProzanWins 23,105 to 16,959
Bill HemengerLoses 15,444 to 7,048
Write-inLoses 14,828 to 176


NameSan Francisco 2010 Municipal Election - District 8
Total Ballots38,551
Input Formatus_ca_sfo
Tabulation Methodeager_irv
Normalized Ballot Dataus/ca/sfo/2010/11/d8/us_ca_sfo_2010_11_d8.normalized.csv.gz

Raw Input Data

File NameSHA-1
Creative Commons License
Created by Paul Butler. The content on this page may be reproduced freely under the terms of the CC BY license.