This paper identies an overlooked implication of models of research joint ventures initiated by d'Aspremont and Jacquemin (1988). Even though the a ggregate R&D cost of identical rms in a research joint venture would be lowest if they invested equally to re- duce subsequent production costs,...

We propose a general estimation principle based on the assumption that instrumental variables (IV) do not explain the error term in a structural equation. The estimators based on the principle is inde- pendent of the normalization constraint, unlike the IV estimators.