Hubs and Clusters in the Evolving U. S. Internal Migration Network

TL;DR

This paper introduces a methodology for analyzing national socioeconomic networks, applied to US internal migration data, revealing key features like hubs and regions and their evolution over 30 years.

Contribution

It develops a two-stage clustering method for weighted, directed networks and applies it to large-scale US migration data to identify and analyze hubs and regions.

Findings

Identification of cosmopolitan hubs and functional regions.

Changes in migration network structure over 30 years.

Validation of the clustering methodology on real data.

Abstract

Most nations of the world periodically publish N x N origin-destination tables, recording the number of people who lived in geographic subdivision i at time t and j at t+1. We have developed and widely applied to such national tables and other analogous (weighted, directed) socioeconomic networks, a two-stage--double-standardization and (strong component) hierarchical clustering--procedure. Previous applications of this methodology and related analytical issues are discussed. Its use is illustrated in a large-scale study, employing recorded United States internal migration flows between the 3,000+ county-level units of the nation for the periods 1965-1970 and 1995-2000. Prominent, important features--such as ''cosmopolitan hubs'' and ``functional regions''--are extracted from master dendrograms. The extent to which such characteristics have varied over the intervening thirty years is evaluated.