Place-to-Place Migration Model

The place-to-place migration model explains and predicts the gross number of people moving from each origin region to each destination region as a function of conditions at both ends and the distance between them. It descends from the gravity analogy popularized by George Zipf in 1946, in which movement between two cities rises with the product of their populations and falls with the distance separating them, but it adds behavioral economic content. Ira Lowry's 1966 formulation is the canonical example: he modeled interregional migration as driven by relative labor-market conditions — wages, unemployment, and the size of the labor force at origin and destination — modified by distance, and estimated the relationship econometrically from observed flows. Cast in log-linear or, in modern practice, Poisson form, the model recovers interpretable elasticities showing how flows respond to a wage gap or an unemployment differential, and it can reproduce or forecast the entire origin-destination matrix. It bridges the descriptive gravity tradition and explicit regression-based migration econometrics, and remains a workhorse for analyzing why people move where they do.