### Flows and Boundaries A Network Framework for Understanding Occupational Mobility in the Labor Market

(with Siwei Cheng)

Although stratification research has long recognized the importance of mapping out the underlying boundaries that govern the flow of workers in the labor market, the current literature faces three major challenges: (1) the determination of mobility boundaries, (2) the incorporation of changes in mobility boundaries, and (3) the incorporation of multi-step flows. The authors propose a network framework that helps address these challenges. The framework conceptualizes the occupational system as a network, in which the nodes are the detailed occupations and the edges are defined by the volume and direction of workers who flow between the nodes. A flow-based community detection algorithm is introduced to uncover the mobility boundaries based on the observed mobility network. Applying this approach to analyze trends in intragenerational occupational mobility in the United States from 1989 to 2015, the authors find that the boundaries that constrain mobility opportunities have become increasingly rigid over time, while, at the same time, decoupled from the boundaries of big-classes and microclasses. Moreover, these boundaries are increasingly sorting workers into clusters of occupations with similar skill requirements. The proposed framework and empirical results illustrate the promise of considering flows and boundaries'' as an analytic basis for understanding the labor market and open up new directions for stratification research.

Keywords: labor market structure, intragenerational mobility, network analysis, boundaries