The paper first extends and reconciles recent estimates of the strikingly large effect of national borders on trade patterns. Estimates comparing trade among Canadian provinces with that between Canadian provinces and U.S. states show interprovincial trade in 1988-90 to have been more than...

Extending McCallum's (1995) result, based on a gravity model of 1988 trade flows, that a typical Canadian province trades 22 times more with other provinces than with U.S. states of similar size and distance, this paper asks how Quebec trade patterns compare with those of other provinces. The...