working papers

1. A dynamic spatial knowledge economy (JMP)

   Cities have long been thought to drive economic growth. Despite this, analyses of spatial policies have largely ignored the effects of such policies on growth. In this paper, I develop a spatial endogenous growth model in which heterogeneous agents make forward-looking migration decisions and human capital investments over the life cycle. Local externalities in the human capital investment technology drive both agglomeration and growth. I show that, along a balanced growth path, the growth rate depends on the spatial distribution of human capital, making it sensitive to spatial policies. I calibrate the model to data on U.S. metropolitan areas and show that it can rationalize the faster wage growth of workers in big cities, as well as other key patterns in life-cycle wage profiles, migration decisions, and city characteristics. Because workers accumulate human capital at different rates depending on where they live, the model provides an environment in which spatial policy can not just attract skilled workers, but produce them, too. I find that policies that further concentrate skilled workers in large cities are growth-enhancing.

2. Agriculture, trade, and the spatial efficiency of global water use (w/ T. Carleton and I. Nath)

   Over 90% of global water use occurs in agricultural production, which is subjective to two pervasive distortions: (i) incomplete property rights for farmers accessing water and (ii) subsidies, taxes, and tariffs affecting agricultural output. This paper combines a rich collection of global geospatial data with a dynamic spatial equilibrium model to quantify the impact of agricultural and trade policies on regional water scarcity and welfare. In the data, we show that water-intensive crops concentrate highly in water-abundant locations, implying a strong role for comparative advantage in governing global water use, though a small number of regions with very water-intensive production are losing water rapidly over time. In the model, we capture production, consumption, and trade in agriculture across many countries and crops, as well as the dynamic evolution of local water stocks as farmers extract from the common pool resource. We calibrate the model to match observed global patterns of agricultural production and hydrological trends and use it to conduct counterfactual simulations of alternative policy regimes. We find that eliminating international trade in agriculture would dramatically increase water depletion across most of the world, and especially so in drier food-importing regions, resulting in large reductions in welfare over time. In contrast, other observed and hypothetical incremental agricultural policy liberalizations have mixed effects that vary greatly across locations, suggesting nuance in implications for policy.

publications

1. Is the world running out of fresh water? (w/ T. Carleton and I. Nath),
   2024, AEA Papers & Proceedings, 114:31–35
   The quantity of water within Earth and its atmosphere is fixed over time, but water available for human consumption evolves dynamically. We use globally comprehensive geospatial data to establish stylized facts about recent changes in global water resources and their potential implications for human welfare. We show that the net change in water volume on arable lands—which account for 90% of human water consumption—is almost exactly zero. Rapid water loss is concentrated in regions with large populations, low existing water resources, and low agronomic potential. Incorporating trade data shows that water-scarce regions are net importers of water-intensive goods.

work in progress

1. Spatial sources of lifetime inequality

   Wage levels and growth vary across locations. How important is this for explaining patterns in lifetime inequality? Risky human capital model with migration and spatial externalities.

2. Slowdown, divergence, and the geography of human capital accumulation

   A (potentially) unified story of the aggregate growth slowdown, regional growth and decline, and micro evidence on migration and human capital investment.

3. Agriculture and the gains from trade (w/ S. Kortum and I. Nath)

   Does trade matter more for poor countries? New ACR-like welfare formula with nonhomothetic preferences + sector-specific trade and income elasticities.

4. Does eating local reduce emissions? (w/ I. Nath, M. Quentel, and J. Sayre)

   Detailed data on emissions from shipping + emissions from agricultural production (by commodity and location) with a quantitative trade model.

5. Trade policy and food security (w/ I. Nath, A. Schmitz, and S. Stewart)

   You’re a policymaker worried about your nation’s food security in an uncertain, global economy — your people can’t eat manufactures, after all. What trade policies, if any, should you set?