"Nonjointness and Scope Economies in the Multiproduct Symmetric Generalized McFadden Cost Function"

The multiproduct symmetric generalized McFadden cost function is increasingly prominent in empirical production analysis. Researchers should be aware that the scope for imposing and testing nonjointness in this model is limited. In the general version of the model, nonjointness requires the nontestable maintained hypothesis of similar (in a sense we define) single-output production technologies, a maintained hypothesis for which there is not normally any basis. The apparent imposition and testing of nonjointness must be qualified accordingly. In restricted versions of the model involving separability or constant returns that are often of interest in applied work,nonjointness is precluded.