In this issue of HSR, the article by Rittenhouse et al. (2004) calls into question two different sources of information about physicians' decisions to leave clinical practice: data from the Physician Masterfile of the American Medical Association (AMA), and physicians' self-reported intentions to leave patient care. The authors conclude that neither source of data provided reliable information on withdrawals from clinical practice. In particular, they find that the AMA Masterfile had a sensitivity of only 9% in detecting physicians who left clinical practice during the previous three years.
One could first respond to this paper by arguing that these findings are neither new nor surprising. The low sensitivity of the Masterfile in recording changes in practice status is attributable to the long reporting lags, which on average can run as long as several years. Thus, the Masterfile cannot be expected to accurately register changes of individual physicians within a time frame shorter than the report lags.
A second, much more appropriate and compelling response is that Rittenhouse et al. point to a major shortcoming in physician workforce data. Reporting lags severely limit what we know about the current size and the geographic and specialty distributions of the physician population. Because of these reporting lags, workforce analyses overestimate both current and future physician supply. These inadequacies must be resolved so that policy analysts can properly assess the adequacy of the physician workforce to meet the nation's demand for physician services.