This paper proposes an approach to measure efficiency of a set of units operating in an administrative public service, namely real estate cadastral offices, which have not been analysed previously. This study has been made possible thanks to the database provided by the Directorate General of Real Estate Cadastral Assessment which includes information on the 52 local offices in Spain for the period between 2000 and 2005. Data Envelopment Analysis has been used to estimate the efficiency levels of these offices. Subsequently, a second stage model based on bootstrap techniques is applied in order to identify other potential factors (differences in management techniques, demographic and economic variables, etc.) that may affect the estimated efficiency measures.