The gravity model is often used to not only explain trade between two countries, but also to investigate the reasons why they don’t. Illustrate this anomaly with suitable examples and reasons....

The gravity model is often used to not only explain trade between two countries, but also to investigate the reasons why they don’t. Illustrate this anomaly with suitable examples and reasons.

Equation (2.1) says that trade between any two countries is proportional to the product of their GDPs. Does this mean that if the GDP of every country in the world doubled, world trade would quadruple?