Temporal scale efficiency in DEA panel data estimations. An application to the solid waste disposal service in Spain

The aim of this manuscript is analyse the long-term scale efficiency of the solid waste disposal service, with the application of a new method for calculating time-invariant and time-variant scale inefficiency using DEA panel data estimates, an approach that allows us to analyse the evolution of scale inefficiency over a period of time. The proposed method is applied to the solid waste collection service for the period 2002-2014 to determine the influence exerted by municipal size and form of service management, over an extended period, on service efficiency. The results obtained indicate that joint management forms obtain greater long-term scale efficiency. In addition, it is established that municipalities with populations between 20,000 and 50,000 inhabitants would improve their long-term scale efficiency if the service were outsourced.