What we do know is that from 1999 to 2003, global foreign exchange reserves rose by more than USD 1.3 trillion to about USD 3 trillion. By far the largest share of this increase is attributable to reserve accumulation in a few countries in Asia as well as in Japan, Russia and Mexico.
These are countries which conduct an exchange rate policy which is either de jure or de facto oriented towards the US dollar. From this development, it could be inferred that most of the reserve accumulation probably pertained to the US dollar.