Exchange Rate Mechanism

The European Exchange Rate Mechanism (ERM) was a system introduced by the European Economic Community on 13 March 1979, as part of the European Monetary System (EMS), to reduce exchange rate variability and achieve monetary stability in Europe, in preparation for Economic and Monetary Union and the introduction of a single currency, the euro, which took place on 1 January 1999.

After the adoption of the euro, policy changed to linking currencies of EU countries outside the eurozone to the euro (having the common currency as a central point). The goal was to improve the stability of those currencies, as well as to gain an evaluation mechanism for potential eurozone members. This mechanism is known as ERM II and has superseded ERM. Currently there is just one currency in the ERM II, the Danish krone.

The ERM is based on the concept of fixed currency exchange rate margins, but with exchange rates variable within those margins. This is also known as a semi-pegged system. Before the introduction of the euro, exchange rates were based on the European Currency Unit (ECU), the European unit of account, whose value was determined as a weighted average of the participating currencies.

A grid (known as the Parity Grid) of bilateral rates was calculated on the basis of these central rates expressed in ECUs, and currency fluctuations had to be contained within a margin of 2.25% on either side of the bilateral rates (with the exception of the Italian lira, the Spanish peseta, the Portuguese escudo and the pound sterling, which were allowed to fluctuate by ±6%). Determined intervention and loan arrangements protected the participating currencies from greater exchange rate fluctuations.

United Kingdom Chancellor of the Exchequer Denis Healey reportedly chose not to join the ERM in 1979 owing to concerns that it would benefit the German economy by preventing the Deutsche mark from appreciating, at the expense of the economies of other countries.

...
Wikipedia