A regional bank is developing a liquidity risk management framework and is evaluating the use of Early Warning Indicators (EWIs) as recommended by the Basel Committee. The Chief Risk Officer presents the following scenario: "Over the past quarter, the bank has observed a noticeable decline in its ability to issue short-term commercial paper, despite offering higher interest rates. Additionally, several institutional counterparties have recently demanded additional collateral for existing transactions. These developments coincide with a 15% month-over-month drop in retail deposit balances." According to the Basel Committee's guidance on liquidity risk EWIs, which of the following indicators is most relevant to the bank's current situation?