The base period of the US dollar index is 65438+March 0973, and the base period of the US dollar index is 100.00, which means that the US dollar index is the result of comparison with 65438+March 0973 at any time. If the US dollar index is 85.75, it means that compared with March 1973, the value of the US dollar has depreciated by 14.25% against a basket of foreign exchange currencies.