Applying Marketing Laws to Social Media: Cross-Cultural Evidence for Duplication of Purchase and Double Jeopardy

Abstract This study examines whether two established empirical generalizations in marketing science, the duplication of purchase and double jeopardy laws, continue to describe user behaviour in social media markets. Social media platforms differ fundamentally from previously studied contexts, as they are characterized by network effects, algorithmic personalization, and near-zero switching costs, all of which create conditions under which classic repertoire-based regularities may break down. Using multiple datasets from more than 4,200 users across two culturally distinct markets, we analyse cross-platform duplication and usage frequency patterns. The results show that platform overlap is systematically related to relative penetration and that platforms with larger user bases also capture a proportionally higher usage frequency. These findings suggest that despite the distinctive structural features of social media, concentration-based behavioural regularities persist. By testing the boundary conditions of established marketing laws in a digitally mediated, networked environment, this study extends quantitative marketing theory and offers implications for strategic media planning in contemporary digital ecosystems.