Estimating the causal effect of offshoring on domestic employment is difficult because of the inherent simultaneity of multinational firms’ domestic and foreign affiliate employment decisions. In this paper, we resolve this identification problem using variation in Bilateral Tax Treaties (BTTs), which reduce the effective cost of offshore activity by mitigating double taxation. We derive a panel difference-in-differences research design from a standard model of multinational firms, demonstrating the simultaneity problem and showing how to resolve it using BTTs as an instrument for offshore employment. We confirm that new treaty implementation is uncorrelated with existing employment trends, and use Bureau of Economic Analysis data on U.S. multinational firms to measure the domestic employment effects of offshore activity.
Overall, we find modest positive effects of offshore activity on domestic employment. A 10 percent BTT induced increase in affiliate employment drives a 1.8 percent increase in employment at the U.S. parent firm, with smaller effects at the industry and regional levels. Underlying these results is substantial heterogeneity based on offshoring margin and firm organizational structure. For example, increased foreign affiliate activity in vertically oriented multinational firms drives declining employment among non-multinationals in the same industry, and multinational firms opening new affiliates exhibit much smaller domestic employment growth than those expanding existing affiliates. Throughout the analysis, OLS estimates are much larger than the IV estimates, consistent with upward simultaneity bias. Overall, our results indicate that greater offshore activity raises net employment by U.S. firms, albeit with underlying job loss and reallocation of workers.