You can do RLAs for IRV

TL;DR

This paper reports the first successful implementation of Risk Limiting Audits for Instant Runoff Voting in San Francisco, demonstrating efficient auditing with a small sample size and providing open-source tools.

Contribution

It introduces a novel process pilot for RLA in IRV elections and provides practical, open-source software for conducting such audits.

Findings

Efficient audit achieved with only 200 ballots sampled

First-ever RLA process applied to IRV elections

Open-source software developed for the pilot

Abstract

The City and County of San Francisco, CA, has used Instant Runoff Voting (IRV) for some elections since 2004. This report describes the first ever process pilot of Risk Limiting Audits for IRV, for the San Francisco District Attorney's race in November, 2019. We found that the vote-by-mail outcome could be efficiently audited to well under the 0.05 risk limit given a sample of only 200 ballots. All the software we developed for the pilot is open source.