A fundamental question in monopolistic competition theory is whether the market allocates resources efficiently. This paper generalizes the Spence-Dixit-Stiglitz framework to heterogeneous firms, addressing when the market provides optimal quantities, variety and productivity. Under constant...

We study the market for applications on Facebook, the dominant platform for social networking and make use of a rule change by Facebook by which high-quality applications were rewarded with further opportunities to engage users. We find that the change led to quality being a more important...

After some decades of relative oblivion, the interest in the optimality properties of monopolistic competition has recently re-emerged due to the availability of an appropriate and parsimonious framework to deal with firm heterogeneity. Within this framework we show that non-separable utility,...

When will a monopolist have incentives to foreclose a complementary market by degrading compatibility/interoperability of his products with those of rivals? We develop a framework where leveraging extracts more rents from the monopoly market by "restoring" second degree price discrimination. In...

We study the repeal of a regulation that imposed maximum wholesale and retail markups for all but five fresh fruits and vegetables. We compare the prices of products affected by regulation before and after the policy change and use the unregulated products as a control group. We find that...

This paper uses a difference-in-difference estimator to test whether the introduction of patient choice and hospital competition in the English NHS in January 2006 has prompted hospitals to become more efficient. Efficiency was measured using hospitals' average length of stay (LOS) for patients...

Case study evidence suggests that exporting firms learn from their clients. But econometric evidence, mostly using exporting and TFP growth, is mixed. We use a UK panel data set with firm-level information on exporting and productivity. Our innovation is that we also have direct data on the...

This review article tries to answer four questions: (i) what are the stylized facts about uncertainty over time; (ii) why does uncertainty vary; (iii) do fluctuations in uncertainty matter; and (iv) did higher uncertainty worsen the Great Recession of 2007-2009? On the first question both macro...