Too strictly interpreted, the Maastricht convergence criteria – the rules for eurozone membership – can begin to look like a suicide pact. The European Union’s newest members are nevertheless required to satisfy them, since they promised on entering the EU that they would eventually join the euro. Unfortunately, the rules keep worthy countries out and lead to policies that are bad for the countries themselves and for Europe as a whole.

To join the euro, countries must keep inflation and interest rates low, stabilise exchange rates for two years and respect the stability and growth pact, which limits the debts and deficits eurozone governments may incur. The rules were adopted for good reasons: members of a currency union must protect themselves against inflation exported from more profligate neighbours.