A Brief History of Banking
6 min read
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Core idea
A bank is not a warehouse for your money. A bank is an intermediary that pools savers' deposits and lends them to borrowers — and in the process, creates new money out of thin air. The trick is called fractional-reserve banking, and once you see it, you can never un-see it. When a bank accepts a $100,000 deposit and lends $90,000 of it to someone else, that lent money gets spent and deposited again — into the same or another bank, which then lends most of that back out. The original $100,000 ripples out as many hundreds of thousands of dollars of new "checking deposit" money, all of it perfectly real, none of it printed on government paper.
This sounds like a magic trick. It is closer to a useful institutional convention: most depositors don't ask for their money on the same day, so it is safe (most of the time) to lend most of it out. The system works because of the law of large numbers and because depositors believe they can withdraw at will. When that belief breaks — a bank run — the magic stops working and the bank fails.
Authors' framing: The most important function of a bank is intermediation between savers and borrowers. The most magical is the creation of money through lending. Both depend on confidence.
Why it matters
Most money is created by banks, not by governments
When the news says "the Fed printed a trillion dollars," that's almost always wrong. The vast majority of the money supply (M1 and M2 from Inconvertible Fiat Explored) is bank-created deposit money, not physical currency. Understanding how lending creates deposits is therefore prerequisite to understanding how money supply changes, why interest rates matter, and why bank failures destroy money rather than merely losing it.
It demystifies the balance sheet
A bank's accounting looks weirdly counterintuitive — your deposit is the bank's liability, not its asset. Once you understand that the bank owes you that money back on demand, the rest of the balance sheet (loans as assets, reserves as assets, equity as the cushion) starts to make sense. And once the balance sheet makes sense, you can read bank earnings, evaluate bank stocks, and understand bank failures intelligently.
It frames everything in Banks as a System — Regulation and Deregulation
The system-level questions in the next topic — interbank lending, the fed funds rate, bank runs, regulation, deregulation, the 2008 and 2023 crises — all sit on top of the mechanics introduced here. Skip this and the next topic feels like alphabet soup.
Key takeaways
Mental model — the timeline of banking
Mental model — how a deposit creates more money
Mental model — a bank's balance sheet
Practical application
Read a bank's earnings report intelligently
Walk through your own deposit
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You deposit $1,000 in your checking account. That $1,000 is now a liability on your bank's balance sheet (it owes you back on demand) and a matching asset (cash or a reserve credit at the Fed).
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The bank keeps a small reserve. Under the post-2020 zero reserve requirement, this is whatever the bank chooses to keep for operational liquidity — typically far less than the old 10%.
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The bank lends most of it out. That lent money is new deposit money in someone else's checking account at some bank. The money supply just expanded.
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The borrower repays slowly. Each principal repayment shrinks the loan asset and removes deposit money from circulation. Over the life of the loan, the money created at origination is gradually destroyed.
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If the borrower defaults, the asset is written down and absorbed by the equity cushion. If too many borrowers default at once, the cushion is exhausted and the bank fails.
Example: a $10,000 mortgage payoff and the missing money
Maria has been making mortgage payments for 25 years. She finally writes a $10,000 check to retire the last of her loan. From her household's perspective: she's debt-free. From the bank's perspective: the asset (her loan) just went to zero, and the liability (her checking account balance) just went down by $10,000 — both sides shrink in lockstep, the balance sheet stays balanced, and the bank earns its accumulated interest from her over the years.
From the economy's perspective, something stranger happened: $10,000 of money disappeared. It wasn't moved somewhere else. It wasn't held by another party. It was simply un-created — the inverse of the act that created it 30 years ago when the bank originated her loan. This is the boring counterpart to bank money-creation: when loans are net repaid faster than new loans are originated, the money supply contracts. That contraction is one of the mechanisms by which recessions get deeper. It also explains why central banks worry so much about credit conditions: if banks stop lending, the money supply shrinks even without the central bank doing anything.
Caveats
Related lessons
Related concepts
- Fractional Reserve Bankinglinked concept
- Money Supplylinked concept
- Interest Ratelinked concept