Data sales and data dilution

We explore indicators of market power in a data market. Markups cannot measure competition, because most data products’ marginal cost is zero, making the markup infinite. Yet, data monopolists may not exert monopoly power because they cannot commit to restricting data sales to future customers. This limited commitment and strategic substitutability of data undermine sellers’ monopoly power. But data subscriptions restore this monopoly power. Evidence from online data markets supports the model's insight that subscriptions indicate market power. Model and evidence reveal that data subscriptions are better for consumers because they sustain the incentive to invest in high-quality data.