New Delhi, March 4 -- High-school physics textbooks tell us that the gravitational pull between two objects is determined by three factors-the weight of the two objects, the distance between them and a universal gravitational constant. The gravitational force is directly proportional to the mass of each object, while it is inversely proportional to the distance between them.

This idea has been successfully adapted in the economics of international trade through the gravity model. Countries tend to trade more with those that are close to them in terms of distance. And the size of economies has a big role to play in determining the volume of trade between two countries. As with the laws of physics, bilateral trade strengthens on the basis ...