A deep dive into the details of China's balance of payments over the last few quarters of data. During the dollar's depreciation in 2017 and the first quarter of 2018, it looks like China was adding to its official assets once again—though the growth largely came from the state banks.
East Asia (China, Japan, and the NIEs) ran a $600 billion current account surplus in 2017. "Official" (central bank and sovereign fund) outflows accounted for about half of that. Asia's foreign exchange market intervention isn't as overt as it once was, but also hasn't entirely gone away.
The U.S. currently runs a surplus on investment income of about 1 percent of GDP, as the income on U.S. equity investment abroad (inflated by tax arbitrage) exceeds the interest the U.S. pays on its external debt. That surplus could shrink significantly as interest rates rise.