This is a compelling story, in part because it paints banking as a scam.
It's also completely wrong and based on myths that have been debunked a million times.
First, the 10% reserve ratio is a relic. Today, reserve requirements in the USA are 0%, yet banks didn't magically start making infinite loans. Why? Because solvent banks are capital constrained, not reserve constrained.
This is where the original story is most misleading.
When a bank receives a $10k deposit (a liability), the sending bank also sends $10k of reserves (an asset). The recipient bank’s Equity (assets minus liabilities) is unchanged. Their lending capacity hasn't improved because their Capital Adequacy Ratio hasn't moved an inch. They don't suddenly have the regulatory room to add $9k of risky new loans to their balance sheet just because they have more cash in the vault.
A bank's capacity to lend is actually contingent on its profitability. If these new deposits are less expensive than their previous funding sources, the bank’s Net Interest Margin improves. Those profits eventually flow into Retained Earnings, which increases their capital. That is what actually creates the capacity to lend more.
This isn't a scam; it's capitalism. Well-managed, profitable banks grow their capital base, which allows them to safely expand their lending to the economy.
The multiplier story is popular because it's simple and cynical. But if you want to understand how the plumbing actually works, follow the capital, not the reserves. 👍
A man deposits $10,000 in a bank.
The bank thanks him and records the deposit on its balance sheet. But not where you might expect. For the bank, that $10,000 is actually a liability – because technically it belongs to the customer and might have to be returned.
So the bank does what banks do. It lends $9,000 of that money to someone buying a car.
Now something interesting happens. The $9,000 loan appears on the bank’s books as an asset – because someone now owes the bank money.
So the same $10,000 is doing two jobs at once. The depositor believes he has $10,000 safely in the bank. The borrower now has $9,000 to spend.
That $9,000 gets deposited somewhere else. The next bank lends $8,100. That gets deposited again. Then $7,290 gets lent out.
Soon the original $10,000 has quietly turned into tens of thousands of dollars of loans scattered across the economy.
Everyone believes they have money. Depositors see balances in their accounts. Borrowers have the money they spent. Banks show healthy assets on their balance sheets because people owe them money.
And here’s the best part.
Banks charge interest on all those loans – maybe 7%. But the depositor who supplied the original money might earn only 0.5% on their savings account.
So banks collect interest on money that mostly wasn’t theirs to begin with – and keep the difference.
The system works beautifully.
As long as nobody asks for the money back at the same time.