It acts as a safety-valve for a country that has an unemployment rate of 20% and no welfare provision.

ECONOMIST: Morocco

They do not have the safety-valve of banking books, where souring assets can escape the rigours of mark-to-market accounting.

ECONOMIST: Investment banking: Is there a future? | The

In the euro's first decade, southern Mediterranean countries enjoyed the benefit of lower interest rates, but they failed to reform their labour and product markets to make their economies more competitive for a world in which they had lost the safety-valve of currency devaluation.

ECONOMIST: Europe and the euro

Or perhaps, since the clever stuff can go wrong, ballot-stuffing is a safety valve.

ECONOMIST: Election fraud