Brigitte Roth Tran

I apply a novel machine-learning based “weather index” method to daily store- level sales data for a national apparel and sporting goods brand to examine short-run responses to weather and long-run adaptation to climate. I find that even when considering potentially offsetting shifts of sales between outdoor and indoor stores, to the firm’s website, or over time, weather has significant persistent effects on sales. This suggests that weather may increase sales volatility as more severe weather shocks be- come more frequent under climate change. Consistent with adaptation to climate, I find that sensitivity of sales to weather decreases with historical experience for precipitation, snow, and cold weather events, but-surprisingly-not for extreme heat events. This suggests that adaptation may moderate some but not all of the adverse impacts of climate change on sales. Retailers can respond by adjusting their staffing, inventory, promotion events, compensation, and financial reporting.

We present a framework to identify market responses to uncertainty faced by firms regarding both the potential incidence of extreme weather events and subsequent economic impact. Stock options of firms with establishments in forecast and realized hurricane landfall regions exhibit large increases in implied volatility, reflecting significant incidence uncertainty and long-lasting impact uncertainty. Comparing ex ante expected volatility to ex post realized volatility by analyzing volatility risk premia changes shows that investors significantly underestimate extreme weather uncertainty. After Hurricane Sandy, this underreaction diminishes and, consistent with Merton (1987), these increases in idiosyncratic volatility are associated with positive expected stock returns.

We use county data from 1980 to 2017 to study the dynamic responses of local economies after natural disasters in the U.S. Specifically, we estimate disaster impulse response functions for personal income per capita and a broad range of other economic outcomes, using a panel version of the local projections estimator. In contrast to some recent cross-country studies, we find that disasters increase total and per capita personal income over the longer run (as of 8 years out). The effect is driven initially largely by a temporary employment boost and in the longer run by an increase in average weekly wages. We then assess the heterogeneity of disaster impacts across several dimensions. We find that the longer-run increase in income per capita is largest for the most damaging disasters. Hurricanes and tornados yield longer run increases in income, while floods do not. The longer run increase in income, which on average has fallen over time, is larger for counties with recent disaster experience. Finally, state-level analyses and estimates of spatial spillovers suggest that, unlike the positive effect for counties directly affected by disasters, the longer run effect of disasters for broad regions as a whole may be negative.

How much, if at all, should an endowment invest in a firm whose activities run counter to the charitable missions the endowment funds? I offer the first model characterizing this type of investment decision. I introduce a strategy called “mission hedging,” where—in contrast to traditional socially responsible investing—foundations may benefit from skewing investment toward the objectionable firm in order to align funding availability with need. I characterize the trade-offs driving foundation investment decisions. By leveraging the idiosyncratic firm risk typically diversified away in profit-maximizing portfolios, foundations may find that bad actors provide good opportunities to hedge mission-specific risks.

Discounting plays a major role in the life cycle of environmental and natural resource policies. Evaluating centuries-scale problems like climate change with standard discount rates yields results that many find ethically unacceptable. Paradoxes abound. Low discount rates are urged for determining the net benefits of climate change, while households fail to undertake energy conservation actions that have payback periods of only a few years. Efforts to uncover discount rates from revealed and stated preferences suggest that a variety of confounding factors may be simultaneously in play. Common property resources provide an example of how market failures can lead to behavior consistent with extreme discounting that can be addressed through effective policy. Finally, politicians who make ultimate policy decisions may have incentives to act in accordance with discount rates not socially optimal.