Migration Space: Doubly Constrained Gravity Model Mapping of Relative Interstate Separation

Abstract

Abstract Absolute physical distances are notoriously bad measures of the relative functional distances that influence the destination choices of U.S. interstate migrants. A novel calibration procedure for doubly constrained gravity models is proposed to map functional relative interstate separations. Doubly constrained models exactly reproduce observed migrant supplies and migrant demands. Using straight-line distances, however, they poorly reproduce the observed state-to-state patterns of flow. The proposed alternative calibration procedure leaves interstate separations as model outputs rather than model inputs. Distances are chosen to replicate observed flows. These distances define a “migration space'’surrounding origin and destination states.