Post

When studying how internal migration affects changes in district-level electoral outcomes, it is important to separate the compositional effect (heterogeneity in political behavior between movers and stayers) from the exposure effect (change in political behavior due to exposure to migration).

We use Rubin's potential outcomes framework to formally define compositional effects and to decompose the total causal effect of internal migration into exposure effects and compositional effects.

These two types of effects are conceptually similar but different to natural (in)direct effects in mediation analysis. We discuss how to identify, estimate, and bound the compositional effect from in- and out-migration.