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...

The contributions of the paper are threefold: i) compare with mathematical rigour the Charnes, Cooper, and Rhodes DEA model and the Farrell model exhibiting constant returns to scale, ii) reinterpret the contribution of Farrell and Fieldhouse that extended the analysis to variables returns to...

Attempts can be found in the DEA literature to identify returns to scale at efficient interior points of the production possibility set on the basis of returns to scale at points of the corresponding reference sets. However, an opposite approach is put forward in this paper, advocating that...