Since the 1990s, efficiency and benchmarking analysis has increasingly been used in network utilities research and regulation. A recurrent concern is the effect of environmental factors that are beyond the influence of firms (observable heterogeneity) and factors that are not identifiable...

The economic and ecological performance of OECD countries over two decades is measured by employing a Malmquist-Luenberger productivity index. The index credits the expansion of goods (value added) and the contraction of bads (emissions), at given inputs. We consider the inputs of capital,...