The index is proportionally weighted based on foreign-exchange trading volume data from the Bank for International Settlements' triennial central-bank survey on global foreign-exchange market activity.

WSJ: WSJ, FX Trader Launch Dollar Index

For another, despite brisk activity in derivatives, foreign exchange and convertible bonds, banks' mainstay businesses have suffered badly.

ECONOMIST: Investment banking

Or to put it another way, the vast majority of foreign exchange trading was supporting market speculation, not genuine wealth-creating activity by businesses.

BBC: How scary is a financial transactions tax?