Figure 1:

Layout of example health systems in the United States showing complex systems (black), a simple system (green), a simple system comprising only of hospitals also known as a medical group (blue), and an independent practice and independent hospital (red). Hospitals and practices are related to their owner (corporate parent or owner subsidiary) via directed edges while owner subsidiaries are related to their corporate parent also via directed edges. The complex system on the far left illustrates that a corporate parent can directly own hospitals and practices as well as owning owner subsidiaries that in turn own hospitals and/or practices. The other complex system illustrates that a corporate parent need not directly own any health units. Systems can also consist entirely of hospitals or practices while the later can be independent.