"The three assessment criteria are: “(1) a significant bilateral trade surplus with the United States is one that is at least $20 billion; (2) a material current account surplus is one that is at least 3 percent of gross domestic product (GDP); and (3) persistent, one-sided intervention occurs when net purchases of foreign currency are conducted repeatedly and total at least 2 percent of an economy’s GDP over a 12-month period.”[1]
https://en.wikipedia.org/wiki/Currency_manipulator