Supplier-induced demand (SID) for health care could be a crucial factor of rising health expenditures. However, there is thus far no consensus on the topic.

To assess how physician density (physician-to-population ratio) and health care consumption correlate.

A systematic review of studies retrieved through electronic databases: Medline, Econlit, PsychINFO and Embase. Search, inclusion and quality appraisal were based on standard procedures and applied independently by two researchers.

Twenty-five studies, generally of moderate quality, were included. Despite a substantial heterogeneity in study design and data modelling, a significant association between physician density and health care consumption was consistently observed. However, estimates varied according to a number of method parameters such as the definition of the dependent variable (physician volume or care intensity), the geographical entity or the medical specialty under consideration, and the adjustment for confounding factors.

The exact importance of SID and the underlying motivations remain poorly understood. We discuss technical issues for better SID assessment. In the absence of more accurate information, limiting physician supply as a measure of cost containment should also be considered cautiously.