China's trade surplus and foreign direct investment (FDI) explain only 30% of this.

ECONOMIST: Capital inflows to China

Dollars are pouring in from China's trade surplus, as well as from foreign direct investment and from speculators betting that China's currency will appreciate.

NPR: Chinese Cash Moves Could Roil Markets

The island runs a large trade surplus, and its foreign reserves are the world's fourth largest, behind China, Japan, and Russia.

FORBES: Taiwan