Here is a useful background piece from the Bloomberg people on the yuan and manipulation

  • President Donald Trump … (US) Treasury Department hasn't accused China of artificially suppressing the value of the yuan because it relies on a 2015 law that sets strict standards for the designation.
  • But a 1988 law -- still in effect -- sets a looser standard. Treasury Secretary Steven Mnuchin simply has to use it, said several former department officials.
  • The U.S. is "looking very strongly at the formula"

Check it out here

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ps. trump has been speaking at a rally in Montana this evening (US time) - he hasn't said too much on China, trade etc. nothing of note anyway. No extra tariffs announced yet.