A NON‐SUBSTITUTION THEOREM WITH NON‐CONSTANT RETURNS TO SCALE AND EXTERNALITIES

An input–output model with non‐constant returns to scale and externalities is presented, and it is shown that in this model the non‐substitution theorem is still valid. More precisely, the quantity side of the theorem, i.e. the proposition on efficiency, remains valid, while there can be no equilibrium prices independent of final demand.