I have recently downloaded a time-series of one-week U.S. Generalized Collateral Repurchase Agreement Rates from Bloomberg (Ticker: USRGCY1Z CURNCY). While looking through the data, I noticed that the bid rate exceeds the ask rate a vast majority of the time. Intuitively, this does not make much sense to me since normally the bid rate is the rate at which a bank is willing to borrow and the ask rate represents the rate that is applied when lending money.
This can be found here: https://financial-dictionary.thefreedictionary.com/Interbank+Bid+Rate
When considering the nature of a GC Repo contract, which is fully collateralized, might the reason be that the collateral (mostly high-quality bonds) are in such high demand that banks "charge" a premium when borrowing?
I am very grateful for any thoughts or hints, thank you in advance!