This book analyses the economic consequences of the regional government of Catalonia's challenge to democracy and the rule of law in Spain. This process, started in 2010, culminated in a coup d'état in the autumn of 2017. The book has three parts. First: The circumstances behind the challenge: economic structure, social and political aspects. Second: The economic impacts of the resulting huge political instability and social polarisation, and the downturn in GDP, investment, competitiveness, Barcelona's appeal, and flight of companies and banks to Madrid. Third: Independence would mean collapse of trade with the rest of Spain and the EU, expulsion from the eurozone, fall of GDP, plummeting tax revenue, soaring unemployment and, finally, conversion of this hypothetical new Catalonia into a failed, vassal and totalitarian state. This book is destined to be the foremost work of reference on the consequences of the separatist threat to Spain, including Catalonia's current decline.