On average, emerging-market central banks hold less than 4% of their foreign-exchange reserves in gold, which is slightly under the 4.6% to 7% mid-range optimal level suggested by previous research done by academics, institutions and the World Gold Council for diversification of reserves.

FORBES: INTERVIEW: Emerging Market Central Bank Gold Allocations Could Rise If Dollar-Based Valuations Removed -- WGC

If, as Mr Sants implied, the new G-SIFI capital increment settles at around 3%, that will be significantly less than the optimal level calculated by David Miles of the Bank of England's Monetary Policy Committee in an influential paper.

BBC: Sants: We wanted banks to hold more capital