The modelling of the interaction between production activities and the natural environment requires formulating a multioutput production function for intended and unintended outputs. The key feature when modelling joint production of intended outputs and unintended residuals is that the latter...

The ratio definition of efficiency has the form of a productivity measure. But the weights are endogenous variables and they do not function as weights in a productivity index proper. It is shown that extended Farrell measures of efficiency can all be given an interpretation as productivity...