Cooper's model for predicting future physician requirements treats the critical determinants of the “right” number of physicians as a black box. His model, like many others, fails to distinguish between the supply of and demand for physician services, and it fails to recognize the important role of price. People who can't agree on the definition of the “right” number of physicians can agree on the “wrong” number: one that causes either shortages or surpluses of health care. People use the terms “shortage” and “surplus” loosely, but the standard economic definitions are clear: A shortage exists when there is unsatisfied demand, which occurs when the quantity of a good or service supplied is less than what people would be willing to buy at the current price. Long waits for elective procedures and for office visits are manifestations of shortage. Conversely, a surplus occurs when there are more willing sellers than buyers at the current price. Unless the demand for physician services is completely independent of price, describing a quantity as too low or too high has no meaning except in relation to its price. The debates about the adequacy of the physician workforce have largely failed to consider price along with quantity. Thus, to address future workforce needs, we must ask how demand and supply will each change and whether price shifts will prevent shortages and surpluses from developing.