Air pollution disperses across political boundaries, yet many environmental policies regulate specific polluted locations. This paper studies how cross-boundary transport of fine particulate matter (PM2.5) changes the welfare effect and optimal design of pollutant control policy in China. Using particle trajectory data from atmospheric transport models, we construct bilateral pollutant-flow matrices that measure the transboundary air pollution in China. Three patterns emerge: (1) Transboundary pollution contributes heterogeneously to local PM2.5, accounting for less than 10% to over 50% of provincial concentrations; (2) Bilateral pollutant transport networks remain stable over time, enabling long-term policy coordination without frequent recalibration; and (3) Economically developed provinces in China receive more transboundary pollution yet achieve larger pollution reduction. We develop a dynamic spatial general equilibrium model that incorporates pollutant transport, trade, and migration. Using this model, we estimate that transboundary air pollution creates a 1% national welfare loss relative to a counterfactual where pollution remains local. We evaluate China's Air Pollution Prevention and Control Action Plan and compare it to alternative allocation rules. Reallocating abatement target to high-spillover upwind provinces based on marginal social welfare of emission tax improves aggregate welfare by 0.18% relative to the actual policy. The findings reveal welfare gains from accounting for spatial externalities in policy design.

Presentations: *PSE Environmental Economics Workshop, UEA North America Annual Meeting, LSE Economics of Energy and Environment Seminar, LSE Trade and Urban Seminar

Trade liberalization can widen gender gaps not only by changing which jobs disappear, but also by shaping who can move into the margins that absorb displaced workers. Using regional variation in exposure to Brazil's 1990s tariff reductions, I show that trade shocks widen gender gaps in employment and earnings. The central margin of adjustment is informality. In more exposed regions, formal employment falls for both men and women, but men are absorbed into informal employment while women are not; instead, women are more likely to leave the labor force. I show that this asymmetry reflects unequal access to adjustment margins. Informal work expands in occupations and sectors where men had stronger baseline access, and stronger male baseline access to informal work predicts a larger gender gap in informal employment responses. Matched employer–employee data reveal a similar mobility gap within the formal sector. Among initially formal tradable workers, men and women experience comparable losses of formal attachment and similar wage losses among those who remain employed, but men are more likely to move across firms and sectors, while women are more likely to remain attached to incumbent employers. Taking together, these results show that trade liberalization creates unequal costs because the margins that buffer displaced workers are themselves gendered.

This paper studies whether national-security enforcement can reshape high-skilled labor allocation. We examine the U.S. Department of Justice's China Initiative and ask whether it reduced U.S. public firms' hiring of Chinese talent. Using firm-level employment histories linked to financial data, we construct pre-policy measures of firms' reliance on Chinese workers and estimate difference-in-differences models comparing high- and low-exposure firms before and after the initiative. Firms with greater pre-policy reliance on Chinese talent reduce the Chinese share of new hires by about 13 percent relative to treated firms' pre-policy baseline. We find no evidence of substitution toward other Asian workers. We find that firms response to the shock primarily through reduced hiring rather than immediate separations of incumbent Chinese employees, and the effects are especially pronounced in strategic technology industries. Worker-level evidence shows that incumbent Chinese workers at more exposed firms do not become more likely to leave their employers after the policy. Instead, they remain attached to those firms while experiencing weaker promotion prospects. The results document a labor-market chilling effect of national-security policy and show that geopolitical policy can alter firms' hiring and workers' career trajectories even without formal employment restrictions.