What happens if the euro collapses? A euro area breakup, even a partial one involving the exit of one or more fiscally and competitively weak countries, would be chaotic. A full or comprehensive break-up, with the euro area splintering into a Greater Deutschmark zone and about 10 national currencies would create pandemonium. It would not be a planned, orderly, gradual unwinding of existing political, economic and legal commitments. Exit, partial or full, would likely be precipitated by disorderly sovereign defaults in the fiscally and competitively weak member states, whose currencies would weaken dramatically and whose banks would fail. If Spain and Italy were to exit, there would be a collapse of systemically important financial institutions throughout the European Union and North America and years of global depression.

Consider the exit of a fiscally and competitively weak country, such as Greece – an event to which I assign a probability of about 20-25 per cent. Most contracts, including bank deposits, sovereign debt, pensions and wages would be redenominated in New Drachma and a sharp devaluation, say 65 per cent, of the new currency would follow. As soon as an exit was anticipated, depositors would flee Greek banks and all new lending governed by Greek law would effectively cease. Even before the exit, the sovereign and the banking system would fail because of a lack of funding. Following the exit, contracts and financial instruments written under foreign law would likely remain euro-denominated. Balance sheets would become unbalanced and widespread default, insolvency and bankruptcy would result. Greek output would collapse.

Greece would temporarily gain a competitive advantage from the sharp decline in the New Drachma’s value, but like Portugal, Spain and Italy, Greece does not have the persistent nominal rigidities to make it a lasting competitive advantage. Soaring wage and price inflation would restore the uncompetitive status quo. Without external funding, imports would collapse, disrupting domestic production. Aggregate demand and aggregate supply would chase each other downwards.