This paper investigates the impact on fiscal revenues of taxing a two‐sided monopolistic platform offering personalized services to users and targeted advertising to sellers, based on the collection of users' personal data. We show that the introduction of a small tax on data collection, which has been proposed in the French context by Collin and Colin, fails to increase fiscal revenues if the value‐added tax (VAT) rate is high enough, due to a tax base interdependence effect between the two taxes. Under a supermodularity condition on the platform's profit function as a function of its prices, this result generalizes to any per‐unit tax. However, in some cases, an ad valorem tax on subscriptions or on advertising may raise fiscal revenues, irrespective of the VAT rate, as well as welfare.

An online platform auctions an advertising slot. Several advertisers compete in the auction, and consumers differ in their preferences. Prior to the auction, the platform decides whether to allow advertisers to access information about consumers (disclosure) or not (privacy). Disclosure improves the match between advertisers and consumers but increases product prices, even without price‐discrimination. We provide conditions under which disclosure or privacy is privately and/or socially optimal. When advertisers compete on the downstream market, disclosure can lead to an increase or a decrease in product prices depending on the nature of the information.

International audienceIn a dynamic model with overlapping generations of consumers, we study duopolistic competition when firms can price discriminate, at each period, between their previous customers and the consumers that they have never served. Long-term contracts are not enforceable. In (Markov-perfect) equilibrium, one firm charges higher prices to its past customers than to its new customers, as past customers have revealed their strong preferences for the firm; the other firm, however, rewards its previous customers by charging lower prices to them than to its new customers. This loyalty reward strategy comes from the interplay between the firms’ usual incentive to extract surplus from consumers with revealed strong preferences and their incentives to acquire information and to recognize their young loyal customers. The result also relies on the firms’ inability a priori to tell different generations apart. It is the outcome of the unique equilibrium of a simplified two-period (or T-period) version of the game and holds with forward-looking consumers who are impatient enough