(3)In order to ensure a level playing field for institutions and derivative markets, the calculation of the additional collateral outflows should be based on the Historical Look Back Approach for market valuation changes developed by the Basel Committee on Banking Supervision (‘BCBS’) for determining those additional collateral outflows, which uses for that purpose the largest aggregated cumulative net collateral outflow or inflow realised at the end of all 30-day periods during the preceding 24 months at the portfolio level.