The index that tracks the U.S. dollar against a basket of six major currencies is the U.S. Dollar Index.
Often identified by its ticker symbol, DXY, the index is a geometrically weighted measure rather than a simple average. Its six components are the euro, Japanese yen, British pound, Canadian dollar, Swedish krona, and Swiss franc. The euro has by far the largest weight, reflecting the structure of the original currency basket.
The index was created by the Federal Reserve in 1973 after the dollar moved into a floating exchange-rate era. Futures trading began in 1985, and ICE Futures U.S. now maintains, calculates, and disseminates the widely traded index. Its base value was set at 100 in 1973, so later readings show the dollar’s movement relative to that starting point.
A frequent mix-up is calling DXY a broad measure of all U.S. trade. It is not: the basket contains only six currencies, and its weights have remained largely unchanged since the euro replaced several European currencies in 1999. The trade-weighted dollar indexes produced by the Federal Reserve use a broader and different set of trading partners.