The weighted average of the bilateral exchange rates for the euro and the currencies of the euro area&#39;s main trading partners. The European Central Bank publishes the nominal effective exchange rates for the euro in relation to two groups of trading partners: The EER-22, made up of the 12 Member States of the European Union that do not belong to the euro area, and the 10 main trading partners outside the EU; and the EER-42, made up of the EER-22 and a further 20 countries. The weightings used reflect the share of each partner in euro-area trade, as well as their competition in third markets. Real effective exchange rates are nominal effective exchange rates deflated by a weighted average of external costs or prices in relation to prices or costs inside the euro area. As such, they are measurements of competitiveness in terms of prices and costs.