Study of the 2024 STV City Council Election in Portland, Oregon

The Data and Democracy lab is excited to announce the release of a report on the 2024 STV City Council Election in Portland, Oregon. In November 2022, voters in Portland, Oregon approved an overhaul to their system of election to use STV or “single transferable vote.” We analyze the mechanics of the STV election to explain that the voting system played a direct role in securing strong representation for communities of color, while several other popular systems of election would have delivered different results when faced with identical voter preferences.

Some highlights from our report include:

No one bloc can sweep in STV

By analyzing how different candidates boosted each other on the ballot, we see the emergence of different blocs of voters. There is strong evidence that as a mechanism, STV prevented any one of these blocs of voters from sweeping a district. We find that the same is not true for other systems of election.

People of color were able to elect candidates of choice

We use statistical inference techniques to determine which candidates were candidates of choice for people of color. We believe we are the first to adapt these techniques to the setting of ranked ballots. This shows that in all four districts, a candidate of choice for people of color was elected. Overall, six candidates of choice were elected to the city council, a remarkable departure from the previous electoral system.

Error rates are moderate and did not impact the ability to elect candidates

We find that the rate of “spoiled” ballots (unable to be counted) was well under 2% in each district, while a large majority of ballots stayed active all the way through the last round of meaningful tabulation. We consider the rates of “STV exhaustion,” where ranking too few candidates deprives a voter of their voice, and of “futility,” where ballots are complete but nonetheless do not contribute to the outcomes, and find that both are quite low. Futility rates in particular are at or under roughly two percent in each district.

You can download our report here.