So you might think that the numbers on your graph are huge. In reality, they are tiny.
Thanks for your reply buddy but I don't understand the bit I quoted. Surely once you take into account the 4.5% the numbers are even larger? Because it means they can lend (excess reserves) / 0.025? Which is ridiculously massive!?
The cash that is held (the 4.5% and i guess the 'excess' 2.5%) is not enough when the economy takes sharp dips. The credit crisis of 2008 and the following global financial crisis was caused mostly by banks not having enough cash. This is why they then go and talk to the central bank to ask for bonds (another form of highly liquid cash). The reason is that when economies and banks collapse, people want to withdraw their money and life savings FAST!
This happened in the UK to a bank called Northern Rock. It was a big bank that took a lot of mortgages. When the crash happened, everyone using the bank went straight to the branch and demanded full withdrawals.
Slight exaggeration here; if 100% of all your depositors ask for their cash back, and you're only holding 7% (4.5+2.5%) of it, then you can see where the problem lies. That cash which is excess, is no longer excess, it never was in the first place.
The term 'excess reserves' is misleading. Perhaps it should be called 'excess over and above the minimum requirements set out by regulators' which in reality is tiny.