On a seasonally adjusted basis, the surplus was 666.5bn yen, well above the 640bn economists had predicted.

BBC: US buying boosts Japanese trade

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?