Most central banks are structuring their reserves portfolios into sub-portfolios, or tranches, to take advantage of different risk and return dynamics as they seek to optimise the management of their foreign exchange assets. The structure and relative size of each tranche tends to be based on expected liquidity needs across a range of time horizons and reserve adequacy scenarios.

On average, 64.9% of the 37 central banks that participated say they tranche their reserves, with the figure rising