Sánchez Cartas, Juan Manuel2026-05-062026-05-062026Sanchez-Cartas, J. M. (2026). The stackelberg–armstrong model. Economics Letters, 265, 113019. https://doi.org/10.1016/j.econlet.2026.1130190165-176510.1016/j.econlet.2026.113019https://hdl.handle.net/20.500.14352/136561We show that sequential (Stackelberg) competition between two-sided platforms can overturn the price-skewness ranking of the Armstrong (2006) competition benchmark: the side subsidized under simultaneous pricing may become the taxed side under sequential play. The mechanism is that the Stackelberg leader internalizes cross-side feedback through the follower’s best response, which introduces both externalities into each side’s markup and can reverse which side is subsidized. The equilibrium is unique, admits closed-form solutions under standard interiority/concavity conditions, and is directly comparable to Armstrong’s benchmark. Both platforms earn strictly more than under simultaneous play, and we characterize a sharp threshold separating second-mover from first-mover advantage.engAttribution-NonCommercial 4.0 Internationalhttp://creativecommons.org/licenses/by-nc/4.0/journal article1873-7374https://doi.org/10.1016/j.econlet.2026.113019open accessL11L81L13Two-sided platformsCompetitionTwo-sided marketsStackelbergEconomía industrial53 Ciencias Económicas