The politicians who are arguing for Catalonia’s independence from Madrid can make a seemingly convincing case that the region would be economically viable as a standalone, sovereign nation. Except that they miss the point. The relative wealth and prosperity Catalonia currently enjoys depends on its links to Spain, the euro zone and the wider European Union. A unilateral breakup would leave Catalonia stranded, and considerably poorer. It would take years before it could become “viable” again.