Shift-share instruments and the impact of immigration

David A. Jaeger, Joakim Ruist, Jan Stuhler

    Research output: Working paper


    A large literature exploits geographic variation in the concentration of immigrants to identify their impact on a variety of outcomes. To address the endogeneity of immigrants' location choices, the most commonly-used instrument interacts national inflows by country of origin with immigrants' past geographic distribution. We present evidence that estimates based on this "shift- share" instrument conflate the short- and long-run responses to immigration shocks. If the spatial distribution of immigrant inflows is stable over time, the instrument is likely to be correlated with ongoing responses to previous supply shocks. Estimates based on the conventional shift-share instrument are therefore unlikely to identify the short-run causal effect. We propose a "multiple instrumentation" procedure that isolates the spatial variation arising from changes in the country- of-origin composition at the national level and permits us to estimate separately the short- and long-run effects. Our results are a cautionary tale for a large body of empirical work, not just on immigration, that rely on shift-share instruments for causal inference.
    Original languageEnglish
    Place of PublicationCambridge, MA
    PublisherNational Bureau of Economic Research
    Number of pages55
    Publication statusPublished - Feb 2018

    Publication series

    NameWorking Paper
    PublisherNational Bureau of Economic Research


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