A common currency for Europe was proposed by Pierre Werner back in 1960. But the euro did not launch until January 4th 1999, with 11 EU member countries participating (Greece has since joined). It began as an electronic currency and an accounting unit, and cash appeared on January 1st 2002.

The euro has both a political and an economic rationale. Integrationists see it as crucial to building an “ever-closer union” among EU members. But others don’t want such union: Denmark rejected the euro in a referendum in September 2000, and Sweden has stayed out for similar reasons. Britain’s Labour government is on the fence: it is waiting for five economic criteria to be met before calling a referendum.

Economically, the euro is meant to complete the European single market, bolstering cross-border mergers, improving price transparency and eliminating exchange-rate risk. Enthusiasts also hope it will be a rival to the hegemonic dollar, against which the euro is approaching parity. Some EU candidates even want to adopt it before full EU membership. But the fledgling currency has dropped in value since its introduction, due largely to (probably overdone) gloom about Europe's economic performance.