About a million years ago I used to teach, amongst other things, "o" level Commerce, to secretarial students ..... they always used to think I was simply making it up when I got to that bit of the syllabus covering banking-- particularly the way banks could, and constantly did, lend out much more money than they actually held as deposits - to the extent governed by the Cash Reserve Ratio set by the Bank of England:
It simply IS the case that banks can and do "create money" out of nothing , all the time - a factor which does have to be strictly controlled by the central bank in a state, or it does indeed produce runaway inflation. Making adjustments to the size of the reserves banks have to hold on to , rather than lend out to new borrowers, is a key part of government economic management. Without the ability of banks to increase the money supply via this "lend more than you have in your vaults as deposits" wheeze, capitalism wouldn't be the dynamically expansive system it has been (most of the time).. and bankers wouldn't have got so very rich ! Of course this entire "upside down pyramid of lending" (balanced on a relatively tiny pile of available cash and easy to liquidate into cash investments) by banks comes seriously unstuck when, Like Northern Rock, the customers lose confidence in the bank and all decide to take their money out -- only to discover it aint in the vaults, it was never all in the vaults .. its been lent out to other people. This "run on the bank" bank collapse happened all over the USA in the 1930's.