On the Use of Proxies in Political Ad Targeting

DOI

Detailed targeting of advertising has long been one of the core offerings of online platforms. At the same time, various actors have abused the detailed targeting ability to show conflicting messages to different groups of people to drive division, polarization, and even social unrest. Platforms have often responded by removing select targeting attributes such as inferred political leaning or ethnicity. In this work we show that major political advertisers in the U.S. circumvented these limitations during the 2022 midterm elections by targeting proxy attributes: seemingly innocuous targeting criteria that closely correspond to political and racial divides in American society. We introduce novel methods for directly measuring the skew of various targeting criteria to quantify their usefulness as proxies. Our findings have crucial implications for the ongoing discussion on the regulation of political advertising and emphasize the urgency for increased transparency.