Currency pair euro has strengthened, or both. On the other hand, if the EUR/USD (or EURUSD) quote changes from 1.2500 to 1.2490 the euro has become relatively weaker than the dollar. The rules for formulating standard currency pair notations result from accepted priorities attributed to each currency. From its inception in 1999 and as stipulated by the European Central Bank, the euro has first precedence as a base currency. Therefore, all currency pairs involving it should use it as their base, listed first. For example, the US dollar and euro exchange rate is identified as EUR/USD. Although there is no standards-setting body
World currency unit have adopted the name "World Currency Unit". The Wocu (contraction of World Currency Unit) is a standardized basket of currencies — the national currencies of the 20 largest national economies measured by GDP, established in 2008. The basket is reweighed semi-annually according to the relative growth of the economies, whereby constituent currencies are replaced by other currencies should the size of the GDP be overtaken by that of another national economy. Conceived as an apolitical and global alternative to the ECU, it is used as a reference currency for global investors and companies seeking to mitigate bilateral exchange rate volatility.