The problem of multiple margins.

The papers in this collection extend the work of John Wennberg and colleagues on variations in the use of health care services and the relationships between variations and health outcomes. Below I explore some theoretical issues that shed light on these observations and reconcile them with other findings in the literature that appear to contradict the work presented here. The analysis centers importantly on the distinction between different types of margins. It is important to understand these differences as a preparation to predicting the outcomes of possible health care reforms.