Uniqueness of Equilibrium in the Multi-Country Ricardo Model
We present two arguments, one based on index theory, demonstrating that the multi-country Ricardo model has a unique competitive equilibrium if the aggregate demand functions exhibit gross substitutability. The result is somewhat surprising because the assumption of gross substitutability is suﬀicient for uniqueness in a model of exchange but not, in general, when production is included in the model.
Scarf, Herbert E. and Wilson, Charles A., "Uniqueness of Equilibrium in the Multi-Country Ricardo Model" (2003). Cowles Foundation Discussion Papers. 1704.