This paper derives the necessary and sufficient condition for the simple gravity equation to hold: the market share of an exporting country is constant across all importing countries. Specialization is just one example satisfying this condition. It holds in a variety of situations where multiple...

This paper constructs a Cournot-Ricardo model of trade by incorporating Cournot competition in a Ricardian trade model. In this model, the share of intra-industry trade in bilateral trade volume decreases as trading partners become more different in terms of the industry distribution of labor...