New Delhi, Aug. 14 -- Do you ever wonder what happens to the trillions of dollars China earns on foreign trade? President Xi Jinping does.

As the No. 2 economy's current account bulges, opportunities for investing the profit domestically shrivel. Excess cash from exports poured into China's property market before Xi's administration more-or-less deliberately crashed it six years ago. Few attractions are left with a 1.7% yield on 10-year sovereign bonds and a stock market that tends to bust after every boom.

The result is massive capital flight, very possibly coming to a data center near you. China ran a record $1.2 trillion trade surplus last year without increasing its official foreign currency reserves, observes Alicia Garcia-Herrero,...