Daily volumes of cash transactions between banks have declined, since many banks don't need to borrow overnight from one another given the relatively large balances they each have in their ES accounts. Indeed, on some days there have been insufficient volumes to calculate the cash rate based on market transactions.
On these days we have instead used expert judgement as set out in our fall-back procedures to determine the published cash rate. These fall-back https://www.rba.gov.au/speeches/2020/sp-ag-2020-07-27.html  4/14  27/07/2020  The Reserve Bank's Operations – Liquidity, Market Function and Funding | Speeches | RBA  procedures ensure that we can continue to publish the cash rate.