Interestingly, the trend can be explained entirely by valuation effects, with the trade-weighted dollar depreciating 4%% in that time frame.

FORBES: Dollar's Share Of Global Reserves Continues To Slide, Reserve Status Questioned

This is a flow variable and so should largely exclude currency valuation effects, but the drawback is that it will usually overstate the amount of official FX intervention as it includes monthly foreign exchange transactions by the PBoC and commercial banks.

FORBES: How Much Longer Can China Accumulate Reserves?

Of the three approaches, methods 1 and 3, using currency shares and empirics respectively to adjust for currency valuation effects, result in robust relationships between changes in currency-adjusted FX reserves and the BOP surplus, whereas method 2 using forex purchases as an alternative proxy for adjusted FX reserves is inferior.

FORBES: How Much Longer Can China Accumulate Reserves?