Using a 3-country Melitz model, we compare the fiscal gains that would result from a hypothetical Catalonian independence with the effect of a hypothetical increase in commercial frictions with the rest of Spain. We find, firstly, that the commercial patterns of Catalonia (seen as an independent country) are, today, qualitatively different to those of any other EU country due to the enormous degree of concentration of commerce in a relatively small partner: the rest of Spain. Our objective is to simulate what would happen if Catalonia became a normal country of the EU. To do so, we calibrate the model for Catalonia, the rest of Spain and the rest of the world; and, also, for Portugal, Spain and the rest of the world. In this way, we can estimate the effective distances (frictions) both between Catalonia and the rest of Spain and between Portugal and Spain. The intellectual experiment that we carry out is to compare the benefits for Catalonia of not paying the fiscal transfer with the costs that would incur if the effective distance between Catalonia and Spain were the same as that between Spain and Portugal. We find that, in this case, the increase of disposible income due to the fiscal saving is lower than the combined effect of greater commercial distortions, a lower productivity of Catalonian firms and, consequently, lower salaries. The net disposible income of the Catalonians would be about 3% lower

Key words: trade costs of independence, border effect, economic integration.
JEL Classification: F14, F15, H70.