Supplier discretion over provision: theory and an application to medical care.

Suppliers who are better informed than purchasers, such as physicians treating insured patients, often have discretion over what to provide. I show how, when the purchaser observes what is supplied but neither the recipient type nor the actual cost incurred, optimal provision differs from what would be efficient if the purchaser had full information, weather or not the supplier can extract informational rent. The analysis is applied to, among other things, data on tests for coronary artery disease and to Medicare diagnosis-related groups defined by the treatment given, not just the diagnosis, illustrating the biases in provision that result.