U.S. Dollar Index

The US Dollar Index (USDX) is an index (or measure) of the value of the United States dollar relative to a basket of foreign currencies.

It is a weighted geometric mean of the dollar's value compared only with

Euro (EUR), 58.6% weight
Japanese Yen (JPY) 12.6% weight
Pound sterling (GBP), 11.9% weight
Canadian dollar (CAD), 9.1% weight
Swedish krona (SEK), 4.2% weight and
Swiss franc (CHF) 3.6% weight
USDX goes up when the US dollar gains "strength" (value) when compared to other currencies.

USDX started in March 1973, soon after the dismantling of the Bretton Woods system. At its start, the value of the US Dollar Index was 100.000. It has since traded as high as 148.1244 in February 1985, and as low as 70.698 on March 16, 2008, the lowest since its inception in 1973.

The makeup of the "basket" has been altered only once, when several European currencies were subsumed by the Euro at the start of 1999.