Such large banks are needed because small players alone cannot make a market. Big banks are also major players in international currency markets, and accumulate major foreign-exchange positions both between their subsidiaries and on a consolidated basis.
大银行之所以有用，是因为光靠小银行是无法做市的。在国际货币市场上，大市场也是主要玩家，它们或者通过支行间的操作，或是以一种坚实的货币为基础，积累起巨大的外汇头寸。