EXPRESS: Within-Category Satiation and Cross-Category Spillover in Multi-Product Advertising

Multiproduct ads (MPAs) allow an ad platform to display multiple products within a single ad unit. Unlike a single-product display ad, similar ads from the same product category may appear in MPAs and induce consumer satiation. Further, the simultaneous display of ads from multiple product categories can result in cross-category complementarity or substitution in consumers’ utility from ad clicking. This study examines ad platforms’ potential benefit from incorporating consumer within-category satiation and cross-category spillover into ad-serving policies. To achieve this goal, the authors propose a full-equilibrium modeling framework to capture both the demand (i.e., consumers’ clicks) and supply (i.e., advertisers’ bids) sides of MPAs. The results from a dataset from a large display ad network reveal heterogeneity in within-category satiation across consumers and categories, and provide evidence of cross-category complementarity. The authors then demonstrate how the platform can indirectly influence the ad variety and category composition of MPAs through three counterfactuals of ad-serving policy changes. The results show that the implementation of a more privacy-preserving policy may hurt both consumer welfare and the platform's revenue because of the reduced ad variety, which makes consumers more prone to within-category satiation and less prone to cross-category complementarity.