President Donald Trump claimed election fraud after losing the 2020 presidential election, and his supporters concurred. Fraud proponents demand the disclosure of ballots. However, concerns regarding the exposure of voter Shinwon make it rare for ballots to be revealed. The situation may change moving forward. It has been confirmed that there is no need to worry about privacy invasion even if ballots are disclosed.
American scientists have revealed that there is virtually no problem protecting voter Shinwon when later disclosing ballots based on the actual presidential election voting results from a certain region. The findings of this study have been evaluated to potentially help increase election transparency. For example, when the number of voters is small, the probability of exposure increases slightly, suggesting that discussions about consolidating or redistricting are necessary.
Researchers from Yale University and the University of California, Los Angeles (UCLA), published results on the 12th (local time) in the international journal "Science Advances," analyzing how the disclosure of ballots impacts voter Shinwon exposure using data from the 2020 general election in Maricopa County, Arizona.
Maricopa County includes Phoenix, the largest city in Arizona. It is as large as some states and has about 4.5 million voters. Notably, Maricopa County is considered a major battleground in the U.S. elections, given its fluctuating voter preference, having supported Trump in 2016, Biden in 2020, and alternating back to Trump in 2024.
After losing the 2020 presidential election, Trump claimed that there was election fraud in Maricopa County. As a result, last year's election saw Maricopa police install metal fences at polling and counting stations and deploy armed guards and drone surveillance due to concerns about potential violence.
The researchers mathematically calculated the probability of voter Shinwon exposure using the 2020 presidential election voting data from Maricopa County. In the U.S., the voter file, equivalent to the electoral roll in South Korea, is disclosed. This voter file includes information such as names, addresses (districts), voting history, and voting methods (mail-in voting, provisional voting, early in-person voting).
The researchers explained that "the ballot records which district and method the vote was cast, and the voter file contains information on which district the individual belongs to and how they voted," noting that "the overlapping information creates a probability of exposing the voter Shinwon." In contrast, in South Korea, the electoral roll itself is not disclosed, and the ballot does not contain information about the district or method of voting, so such a probability does not exist in the first place.
If voters using the same voting method in the same district unanimously supported a specific candidate, it becomes evident who the voter voted for. Even if there is not a unanimous vote, the probability of voter exposure exists. In a group of 20 voters where 19 voted for Trump and 1 voted for Biden, if one of them reveals, "I voted for Biden," it discloses the identity of the 19 voters who voted for Trump.
The researchers calculated these various situations of voter exposure as probabilities. As a result, the probability of voter exposure when only the election results are disclosed was just 0.00009%, virtually zero. However, when counting data by district along with voting method data were disclosed, the exposure probability increased to 0.05%.
Finally, when even anonymized individual ballots were disclosed, the probability of Shinwon exposure rose to 0.17%. This means that even with the disclosure of ballots, 99.83% of voters' Shinwon are still protected.
According to the paper, cases with high probabilities of exposing voter Shinwon concentrated in areas with 30 or fewer voters among the 743 precincts in Maricopa County. The researchers noted, "By consolidating or redistricting to prevent unanimous votes within specific districts, the probability of voter exposure can also be reduced."
Shiro Kuriwaki, a professor at Yale University who led the study, stated, "It is becoming important to find a balance between the transparency of election results and the protection of voter privacy," adding that "the findings of our analysis will provide a critical framework for increasing the transparency of election results."
References
Science Advances (2025), DOI: https://doi.org/10.1126/sciadv.adt1512