The Australian Securities Exchange has been appointed as the new administrator of the bank bill swap rate benchmark. The ASX will take over from the Australian Financial Markets Association in January.The ASX and AFMA will work together during a transition period, moving to the new volume weighted average price calculation methodology.ASX was chosen in a tender process conducted by EY.The market has relied up to now on a best bid and best offer calculation methodology. Under the new arrangement there will be a "calculation waterfall", starting with a calculation of the volume-weighted average price of primary issuance and secondary trading of eligible securities within a trading window defined as 9am to 10.10am.If that process fails, the market will fall back on the best bid and best offer method, using live executable bids and offers to calculate BBSW.AFMA's changes are part of global reform of interest rate benchmarks and were guided by proposals put forward by the Council of Financial Regulators.The CFR said that to ensure BBSW remains a trusted, reliable and robust financial benchmark it should be anchored to transactions in an active underlying market.