This paper examines spatially-correlated multilevel models from formal/mathematical and empirical perspectives. Multilevel (or variance components) models have been applied in many areas of regional science, school effect estimation, epidemiology, and polimetrics. They are most often used to model treatment nonstationarity in policy regimes, a form of spatial process heterogeneity. Multilevel models with spatially-correlated components are increasingly used to model the joint presence of spatial heterogeneity and spatial dependence. Previous treatments typically focus on stating a single spatial multilevel specification, deriving its estimators, and demonstrating its properties in a case study. Instead, a more general approach is possible. To do this, we derive the "shrinkage matrix," which directly expresses the relationship between single-level model estimates and their multilevel analogues. We show that this shrinkage matrix results in regional spatial spillovers, a substantial novel behavior. We provide an empirical example that demonstrates this behavior: identifying state-specific factors influencing endoscopy use among Medicare participants. Due to the complexity of tradeoffs between dependence and heterogeneity in even simple spatial multilevel models, we suggest more formal attention is needed to build transferable insight in this area. *