This paper, by using conditional directional distance functions as introduced by Simar and Vanhems [J. Econometrics 166 (2012) 342–354] modifies the model by Färe and Grosskopf [Eur. J. Operat. Res. 157 (2004) 242–245] and examines the link between regional environmental efficiency and...

This paper proposes a conditional directional distance function estimator in order to examine the link between regional environmental efficiency and GDP per capita levels. As an illustrative example we apply our model to US regional data revealing an inverted ‘U’ shape relationship between...

In this work, we analyze the performance of production units using the directional distance function which allows to measure the distance to the frontier of the production set along any direction in the inputs/outputs space. We show that this distance can be expressed as a simple transformation...