Gravity equations have been used for more than 50 years to estimate ex post the partial effects of trade costs on international trade flows, and the well-known - and traditionally presumed exogenous - "trade-cost elasticity" plays a central role in computing general equilibrium trade-flow and...

We review and interpret the main theoretical developments in the gravity literature from its very early, a-theoretical applications to the latest structural contributions. We also discuss challenges and implement methods to estimate empirical gravity equations. We finish with a presentation and...