The Chinese Yuan is "stabley" depreciating at a ~20% annualized rate, at a current cost of $1.3 trillion per year in FX reserves, based upon December and January data:
CNBC: Jan. 7, 2016
FX Reserves Drop Record $108 billion In December
$108 billion annualized is $1.3 trillion. They spend $5 billion per trading day defending the "free floating" currency.
As we see below, the currency depreciated by almost an identical approximately -1.5% in December and January, which is -20% compounded over 12 months. Therefore at a current $3.3 trillion in reserves, best case scenario, they have $2 trillion in reserves in a year from now and a 20% depreciation. If they attempt to slow depreciation, they burn more reserves.
Oil is ~10:1 leveraged to the Chinese Yuan:
Yuan with oil:
Oil fell -28% during the same two months with a 95% correlation (except when the currency was held "stable")...
