U.S. farm labor markets have tightened sharply over the past decade, with rising real wages, persistent harvest-season labor shortages, and a less mobile workforce (Charlton et al., 2019; Fan et al., 2015; Hertz and Zahniser, 2013). Over one-third of U.S. farm workers are unauthorized immigrants, and intensified interior immigration enforcement has reduced the supply of settled non-citizen agricultural workers in affected jurisdictions (Kostandini et al., 2014; Charlton and Kostandini, 2021). Over the same period, certifications under the H-2A agricultural guestworker program, which allows U.S. employers to hire foreign workers for seasonal farm jobs, grew fivefold. This paper estimates how much of the H-2A expansion is causally attributable to the contraction of settled non-citizen farm labor. Using a panel of 740 commuting zones over 2008–2024, I implement a Bartik shift-share instrumental variables design that exploits cross-sectional variation in baseline settled-worker exposure interacted with national enforcement shifts. Our estimates show that for each settled non-citizen agricultural worker lost, farms hire approximately two H-2A guestworkers, accounting for about 48 percent of aggregate H-2A growth over the period.
