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How Banks Create Money

Here is one of economics' most disorienting truths: most of the money in your country was not printed by anyone — it was conjured into existence by ordinary banks, the moment they made loans. This guide walks the magic trick slowly, then shows where the textbook story bends.

The sentence that should startle you

In the last guide you met the [[commercial-bank|commercial bank]] as a clever middleman: it gathers deposits from savers and, under fractional-reserve banking, keeps only a slice in the vault and lends the rest to borrowers. That picture is right but quietly incomplete, and the missing piece is astonishing. When a bank makes a loan, it does not hand over someone else's saved-up cash. It writes a new number into the borrower's account — and that number is brand-new money that did not exist a second before.

Recall what counts as money. From the money supply guide, the deposit balance in your bank account *is* money — it sits squarely inside the everyday measures like M1 and M2. So when a bank credits a borrower's account with, say, 100,000 for a car, the country's money supply has just risen by 100,000. No printing press ran; no coins were minted. A keystroke did it. This is [[money-creation|money creation]], and the overwhelming majority of the money circulating in a modern economy was born exactly this way — as the flip side of someone taking out a loan.

Following one coin through the system

The classic textbook story shows how *one* injection of real cash ripples into a much larger pile of deposit money. Suppose the central bank puts 1,000 of fresh cash into the system — this base cash is the [[monetary-base|monetary base]] — and every bank is required to keep 10 percent of its deposits as reserves. That 10 percent is the [[reserve-ratio|reserve ratio]]. Watch the cash travel.

  1. Amir deposits 1,000 in Bank A. Bank A keeps 100 as reserves (10 percent) and lends 900 to Bina. Money supply so far: Amir's 1,000 deposit plus Bina's 900 loan = 1,900.
  2. Bina spends the 900; whoever she pays deposits it in Bank B. Bank B keeps 90 and lends 810 onward. New deposit money added: 810.
  3. That 810 gets spent and re-deposited in Bank C, which keeps 81 and lends 729. And so the wave rolls on, each round 90 percent of the one before.
  4. Add up every round — 1,000 + 900 + 810 + 729 + … — and the shrinking pieces sum to a finite total: 10,000 of deposits, built on just 1,000 of original cash.

Nothing dishonest happened at any single bank. Each one held its required reserves and lent only what it could. Yet the *system* turned 1,000 of cash into 10,000 of money. That is the heart of fractional reserves: because not everyone withdraws at once, the same base cash can sit behind many layers of deposits simultaneously. Each loan becomes the next bank's deposit, which funds the next loan — a chain of credit standing on a thin foundation of cash.

The money multiplier, in one fraction

You do not have to add up an endless chain by hand. That shrinking geometric series collapses into a single neat number, the [[money-multiplier|money multiplier]]: the maximum amount of deposit money the system can build on each unit of base money. In the simplest case it is just one divided by the reserve ratio. A 10 percent reserve ratio gives a multiplier of 1 / 0.10 = 10 — exactly the 1,000-into-10,000 we just traced. The lower the reserve ratio, the more rounds of lending each coin survives, and the taller the tower of money it can support.

money multiplier  =  1 / reserve ratio

   reserve ratio 10%  ->  1 / 0.10 = 10x   (1,000 base -> up to 10,000 money)
   reserve ratio 20%  ->  1 / 0.20 =  5x   (1,000 base -> up to  5,000 money)
   reserve ratio  5%  ->  1 / 0.05 = 20x   (1,000 base -> up to 20,000 money)

   These are CEILINGS, not guarantees:
     - banks may hold extra reserves they don't lend out
     - people may hold cash instead of redepositing
   Either leak makes the real-world multiplier SMALLER.
The multiplier is a ceiling, not a promise. It tells you the most money the system could build — reached only if every bank lends right to its limit and every coin returns as a deposit. In the real world, both leak.

Two leaks keep the real multiplier well below the textbook ceiling. First, banks often choose to hold excess reserves — more than the law requires — when they are nervous or short of safe borrowers, and idle reserves create no new deposits. Second, people pull some money out as cash and stuff it under the mattress instead of redepositing it; that cash leaves the lending chain entirely. After 2008, banks in several countries piled up vast excess reserves, and the textbook multiplier badly over-predicted how much the money supply would actually grow. The fraction is a useful skeleton, not the living body.

Which comes first — reserves or the loan?

Now the honest, more modern twist — and it is a real debate, not a footnote. The chain we just walked makes it sound as if reserves come *first*: cash arrives, then banks lend a multiple of it, as though reserves were the fuel and loans the exhaust. But many central banks now describe the causation as running the *other way*. A bank does not check its vault before lending to a creditworthy customer; it makes the loan first — creating the deposit with a keystroke — and then, if it ends up short of required reserves, it *borrows* them afterward, from other banks or from the central bank itself.

In this view, lending is limited not by a fixed pile of reserves but by something more alive: how many borrowers are willing and creditworthy, how profitable the loan looks, and the bank's own capital and risk appetite. The central bank still steers the whole thing, but mainly through the *price* of money — the interest rate it charges banks for reserves — rather than by rationing a fixed quantity. The Bank of England put it bluntly in a 2014 paper: in the modern economy, most money is created by commercial banks making loans, and the simple multiplier story 'is not an accurate description.' That is a striking admission from a central bank about its own textbooks.

Why this plumbing matters

Seeing money as bank credit reframes nearly everything that follows. When banks lend eagerly, deposit money swells, spending picks up, and — if it outruns what the economy can produce — prices climb; that is one face of inflation, which the next rung explores. When banks pull back in fear, money can *shrink*: loans get repaid faster than new ones are made, deposits evaporate, and a credit crunch can choke an economy even though no cash was physically destroyed. Booms and busts in lending are, quite literally, expansions and contractions of the money supply.

It also exposes the system's fragility, which the final guide in this rung tackles head-on. If a bank's money is mostly other people's deposits that it has lent away, it can never repay all depositors at once — that is the seed of a bank run. And it explains why, when the chain seized up in the 2008 crisis, central banks reached for tools like quantitative easing to pump in base money directly, hoping to coax frightened banks back into lending. The whole apparatus of banks, reserves, and the reserve ratio is the hidden plumbing under interest rates, inflation, and financial crises alike.