Here is my understanding:
The European Central Bank (ECB) deposit rate is the interest rate the ECB gives a bank for holding a deposit with them.
Currently this rate is -0.5%. Which means that it costs the bank money to put a deposit with the ECB. This is presumably to encourage lending.
Additionally any “excess liquidity” is treated the same as a deposit to the ECB. Excess liquidity is any amount of money a bank has on its balance sheets above the reserve requirements.
Therefore… if a bank could lend someone money at 0.0% interest rate, then they should, because otherwise the bank is paying the ECB essentially a penalty of 0.5% .
This all makes sense so far. Now comes the EURIBOR 1-week rate. As I understand it, this is a rate that essentially summarizes the interest rates that bank charge to lend money to one another. So far so good. But… the Euribor 1-week rate is currently -0.563% — which is lower than the deposit rate!!
I just can’t understand this. That means if a bank does nothing it loses -0.5% for holding a deposit, but if it lends the money out it loses -0.563%, which is more. Why would this ever happen?
EDIT: Not only that but the ESTER rate - the overnight interbank rate - is -0.579% !