Public procurement markets are often national a general agreement national preferencing. I exploit shocks occurring during the Covid-19 pandemic to two important factors, , measured through local infection rates, and increased , to study home bias in public procurement. Two causal difference-in-difference analyses on novel data for medical supplies in Europe show that home bias is not inevitable. An increase in local infection rates by one standard deviation locally increases the share of cross-border procurement by 19.3 percentage points over a baseline of 1.5 percent. Also, deregulation that allowed for buyer discretion caused cross-border procurement to increase by more than 35 percentage points. A simple theoretical model systematizes these findings.

In Goodkin-Gold et al. (2021), we analyzed optimal subsidies for a vaccine against an epidemic outbreak like Covid-19. This companion paper alters the underlying epidemiological model to suit endemic diseases requiring continuous vaccination of new cohorts-also suiting an epidemic like Covid-19 if, following Gans (2020), one assumes peaks are leveled by social distancing. We obtain qualitatively similar results: across market structures ranging from perfect competition to monopoly, the subsidy needed to induce first-best vaccination coverage on the private market is highest for moderately infectious diseases, which invite the most free riding; extremely infectious diseases drive more consumers to become vaccinated, attenuating externalities. Stylized calibrations to HIV, among other diseases, suggest that first-best subsidies can be exorbitantly high when suppliers have market power, rationalizing alternative policies observed in practice such as bulk purchases negotiated by the government on behalf of the consumers.

This paper analyzes two business practices on the mobile internet market, paid prioritization and zero-rating. These practices allow the internet service provider to discriminate different content types. With prioritization, the ISP delivers content at different speeds; with zero-rating, the ISP charges different prices. In recent years these practices have attracted considerable media attention and regulatory interest. When the asymmetry between content providers is limited, in particular with regard to their ability to attract traffic or to monetize it, we first show that the ISP can extract more surplus from consumers by privileging the relatively weaker content and restoring symmetry between content providers. Next, we show that the ISP chooses prioritization when traffic is highly valuable for content providers and congestion is severe, and zero-rating in all other cases. Finally, we find that a policy banning prioritization can lead to zero-rating and a reduction in consumer surplus.

Insurance induces a tradeoff between the welfare gains from risk protection and the welfare losses from moral hazard. Empirical work traditionally estimates each side of the tradeoff separately, potentially yielding mutually inconsistent results. I develop a nonlinear budget set model of health insurance that allows for both simultaneously. Nonlinearities in the budget set arise from deductibles, coinsurance rates, and stoplosses that alter moral hazard as well as risk protection. I illustrate the properties of my model by estimating it using data on employer sponsored health insurance from a large firm.

One of the most conspicuous features of mergers is that they come in waves that are correlated with increases in share prices and price/earnings ratios. We use a natural way to discriminate between pure stock market influences on firm decisions and other influences by examining merger patterns for both listed and unlisted firms. If "real" changes in the economy drive merger waves, as some neoclassical theories of mergers predict, both listed and unlisted firms should experience waves. We find significant differences between listed and unlisted firms as predicted by behavioral theories of merger waves.

In the absence of an effective antitrust law, both fare wars and price collusion have been pervasive in China's airline markets, causing concern for both airlines and consumers. A study of monthly airfare data from 2002 to 2004 confirms that fare wars occur periodically, as well as price collusion. Both tend to be short-lived. The fact that collusion is more likely to occur in January and April when demand is high, as revealed by China Eastern's and China Southern's price-war and collusion models, has been confirmed by interview information obtained from the airlines' sales managers. However, there is also evidence in these models suggesting that collusion can be more easily formed when demand is low. High airport concentration measured by the HHI may facilitate collusion in certain circumstances, but it may also lead to more price wars under other conditions. Concentration in both airports and routes does not appear to systematically affect the occurrence of fare wars and collusion in all the models estimated. We also reject the possibility that mutual forbearance due to multimarket contact plays any important anti-competitive role in China's airline markets.