The weighted average of the bilateral exchange rates for the euro and the currencies of the euro area'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.