Building path diagrams for multilevel models

Multilevel models have come to play an increasingly important role in many areas of social science research. However, in contrast to other modeling strategies, there is currently no widely used approach for graphically diagramming multilevel models. Ideally, such diagrams would serve two functions: to provide a formal structure for deriving the underlying equations and to provide a mechanism for clearly and efficiently communicating the model structure, assumptions, and empirical results. Here the authors propose a path diagramming approach for multilevel models that seeks to meet these goals. The authors begin with a description of the core components of their proposed diagramming system and establish tracing rules for the direct derivation of model equations. They then demonstrate their approach using several published empirical multilevel applications and conclude with potential limitations and directions for future developments.