When the quality of a good varies, quantity in physical units may be a very misleading measure of total consumption. In this paper it is argued that differences in quality are a distinguishing feature of the market for physicians' services. We develop a model to analyze properties of demand functions for the quantity and quality of physicians' services and apply the model to study the demand for pediatric care--physicians' services rendered to children. The theoretical model of quantity-quality substitution provides a framework for demand analysis whenever the market for a good is distinguished by a quality component.

When the quality of a good varies, quantity in physical units may be a very misleading measure of total consumption. In this paper it is argued that differences in quality are a distinguishing feature of the market for physicians' services. We develop a model to analyze properties of demand functions for the quantity and quality of physicians' services and apply the model to study the demand for pediatric care--physicians' services rendered to children. The theoretical model of quantity-quality substitution provides a framework for demand analysis whenever the market for a good is distinguished by a quality component.