The Bank of England published a supplementary consultation paper on its revised proposed averaging methodology to be used for the Sterling Overnight Index Average Interest Rate Benchmark, known as SONIA. The BoE took over as administrator of SONIA on April 25, 2016. SONIA is currently based on a market for brokered deposits which has limited transaction volumes. In October 2016, the BoE consulted on its proposals to reform SONIA in four areas, including the SONIA calculation methodology. The Bank proposed to switch the current calculation to measuring the average rate using a volume-weighted median, rather than a volume-weighted mean. Following feedback to that proposal, the BoE is now proposing that SONIA be calculated as the volume-weighted trimmed mean rate of eligible transactions. This is calculated by removing transactions at outlying rates and calculating the mean of the remaining transactions.

Responses to the consultation are due by March 16, 2017. By the end of March 2017, the BoE intends to publish its final approach to the design of SONIA and the transition and publication arrangements in a summary and response to feedback document which will cover both this consultation and the October 2016 consultation. The BoE had intended to transition from the current benchmark to the proposed reformed SONIA between October and December of 2017. However, the BoE now expects that the transition will take place in March or April 2018.

View the consultation paper.