The Georgia 2020 Risk-Limiting Audit with VotingWorks

November 11, 2020 — Ben Adida

VotingWorks is a non-partisan non-profit building secure & affordable election technology. One of our key contributions is in the deployment of risk-limiting audits. A risk-limiting audit is the gold standard of tabulation audits, where a randomly selected sample of ballots is reviewed by audit boards. A risk-limiting audit tells us that, if all ballots were counted by hand, the winner declared by the tabulators would be confirmed. VotingWorks provides states with support and open-source software to run risk-limiting audits.

Over the last year, VotingWorks has been assisting Georgia with their implementation of risk-limiting audits. We ran a few pilots in Georgia counties following the Presidential Primary earlier this year. Georgia is one of a small set of states at the head of the pack in the deployment of risk-limiting audits, and we’re proud to be helping them.

The preliminary vote count for Georgia indicates today that Joe Biden won the election with a margin of approximately 14,000 votes, or roughly 0.3%. This is a fairly tight margin of victory. When a risk-limiting audit is performed, the number of ballots examined is based on the margin of the contest: a tight margin requires a significantly larger sample size, while a wider margin means fewer ballots can be examined. In Georgia’s case this year, the required sample size is so large – more than 1.5M ballots – that it is less work to sample every cast ballot, simply because attempting to audit a large subset incurs the work of retrieving and replacing specific ballots, while reviewing all ballots does not.

Thus, we expect the Georgia RLA this year to require audit boards across the state to examine every cast ballot. This will be a large amount of work, and we’re proud to be supporting Georgia in their dedicated endeavor to verify that the claimed winner is indeed the true winner. We’re also particularly proud of the transparency of this entire process: the software we use is open-source, the math has been vetted by academics for a decade, and the process of reviewing ballots is open to the press and the public.