EXPRESS: Consumers Believe Legal Products Are Less Effective than Illegal Products

This research examines how consumers judge a product’s effectiveness based on its legal status. Across eight pre-registered experiments, we find that consumers tend to believe legal products are less effective than illegal ones. Even when observing identical, objective product outcomes (e.g., equal weight loss from a drug), consumers perceive reduced product benefits from a product described as legal (vs. illegal). We test an account of why this belief occurs. When a product is legal, consumers infer that the government allows broad access to it, which they associate with lower product strength. In contrast, illegal products, which consumers presume are harder to access, are viewed as higher in product strength. This strength inference leads consumers to believe a legal product produces smaller effects than an illegal product—both smaller positive effects (lower efficacy) and smaller negative effects (lower harm). Supporting this theory, the impact of legality on perceived efficacy is eliminated if legal and illegal products are described as equally accessible or equally strong. We further demonstrate that these beliefs influence consumer choice. Given the significant health and economic consequences of illegal product consumption, this research has important implications for consumers, marketers, public health professionals, and policymakers.