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This paper provides the first nationwide U.S. evidence on the effects of electric vehicle (EV) adoption on air quality and child health. Using county-level data from 2010–2021, we link EV registrations to air pollution, birth outcomes, and emergency department visits. Endogenous adoption is addressed using two-way fixed effects and an instrumental variables strategy exploiting the rollout of federally designated Alternative Fuel Corridors. Greater EV adoption significantly lowers nitrogen dioxide and improves infant and child health, reducing very low birth weight, prematurity, and asthma-related emergency visits. The largest health gains occur in high-pollution areas and exceed $1.2–$4.0 billion annually.

Purely affective interaction allows the welfare of an individual to depend only the individual’s own action and on the profile of welfare levels of others. Under an assumption on the structure of mutual affection that we interpret as non-reinforcing mutual affection, we show that equilibria of affective interaction are Pareto optimal. Moreover, if purely affective interaction induces a standard game, then an equilibrium profile of actions is a Nash equilibrium of the induced game, and this Nash equilibrium and Pareto optimal profile of strategies is locally dominant.

Human capital is central to efforts to promote growth, convergence, and the elimination of poverty. Drawing on seminal macroeconomic frameworks by Nelson-Phelps, Lucas, and subsequent developments, alongside macro and microeconomic evidence, the chapter examines the role of human capital in driving innovation and growth, emphasizing how different types of human capital matter at different stages of development, and discussing obstacles to accumulation and evidence from policy interventions.

High-dosage tutoring has the potential to substantially raise adolescent academic achievement, but schools may lack the resources to deliver small-group tutoring frequently at scale. This paper studies the relative importance of tutoring group size (quality) versus tutoring frequency (quantity) using a randomized controlled trial in a Midwestern U.S. charter middle school. Students were randomized to a control group, tutoring twice a week in 2-student groups, or tutoring three times a week in 3-student groups, with equal total cost per student across the two treatment arms. The results show that tutoring in 2-student groups led to a statistically significant improvement in math skills of 0.23 standard deviations, while the more frequent 3-student group tutoring did not produce significant gains. The findings suggest that, under budget constraints, smaller group size may be more effective than higher frequency.

We develop an integrated framework for information design and mechanism design in screening environments with quasilinear utility. Using the tools of majorization theory and quantile functions, we show that both information design and mechanism design problems reduce to maximizing linear functionals subject to majorization constraints. For mechanism design, the designer chooses allocations weakly majorized by the exogenous inventory. For information design, the designer chooses information structures that are majorized by the prior distribution. When the designer can choose both the mechanism and the information structure simultaneously, then the joint optimization problem becomes bilinear with two majorization constraints. We show that pooling of values and associated allocations is always optimal in this case. Our approach unifies classic results in auction theory and screening, extends them to information design settings, and provides new insights into the welfare effects of jointly optimizing allocation and information.

Many seemingly different economic problems share a common mathematical structure: they involve the maximization of a functional over sets of monotonic functions that are either majorized by, or majorize, a given function. This paper presents new, simpler proofs for the main characterization results of the extreme points of sets defined by monotonicity and majorization constraints obtained by Kleiner, Moldovanu, and Strack (2021). It demonstrates how these characterizations can be applied to a broad range of economic applications, including auction and information design, contest design, optimal delegation, optimal stopping, and decision problems under risk. The paper concludes with an overview of recent related work extending these characterizations to settings with additional constraints, multidimensional state spaces, and alternative stochastic orders.

This chapter, prepared for the Handbook of Development Economics (Vol. 6), reviews recent microeconomic evidence on the causes of resource misallocation in developing countries. It distinguishes between “technological” and “distortionary” wedges, develops a unified theoretical framework linking market power, taxes, financial frictions, and firm dynamics, and summarizes empirical findings from the “direct approach” to misallocation. The authors emphasize how wedges vary by firm size and discuss policy implications for improving allocative efficiency.

We examine the impact of firearm violence on newborn health in the U.S. using two approaches. First, we analyze the "beltway sniper" attacks in 2002, leveraging both temporal and spatial variation to compare birth outcomes of exposed children to those unexposed. Second, we investigate in-utero exposure to mass shootings using national data. We find that exposure to these incidents during pregnancy increases the likelihood of very low-birthweight and very premature birth. These events carry a significant economic burden, with the beltway sniper attacks costing at least $155 million and mass shootings resulting in annual costs exceeding $75 million.