Una introducción al análisis multinivel: ¿La demanda individual de salud es afectada por el médico de cabecera?

The purpose of this paper is to analyze the multilevel methodology in order to estimate the effect of primary care physician in the pharmaceutical expenditure of the patient. We use individual data from population that is part of the Spanish public health system in the Autonomous Community of Aragón in 2004. For the city of Zaragoza, our results show the existence of a random effect significant of the primary care physician in spending made by patients. The large proportion of zeros in the sample requires a correction for selection bias. The application of Heckman’s model provides evidence of this bias, although the main results do not differ. Estimating a censored model with multilevel structure called a topic of particular interest.