Chapter 12: A Brief History of Banking

Book: Economics 101

Author: Alfred Mill & Michele Cagan

Type: Chapter

Category: Economics

Difficulty: Beginner

Reading time: 9 min

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 chapter 10) 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 chapter 13

The system-level questions in the next chapter — 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 chapter feels like alphabet soup.

Key takeaways

Key takeaways

• Banking is ancient. Egyptian and Mesopotamian temples and granaries operated as proto-banks 4,000 years ago, taking deposits and keeping records.
• Renaissance Italian city-states ran the first recognizably modern banks, using clever instruments like the bill of exchange to charge interest while technically respecting the Church's ban on usury.
• English goldsmiths invented fractional-reserve banking when they realised they could issue more receipts than they had gold on deposit — because depositors rarely demanded all the gold at once.
• Banks serve three core functions: safe storage of wealth, facilitating trade (via checks, debit/credit cards, transfers), and intermediating between savers and borrowers.
• A bank's balance sheet follows Assets = Liabilities + Equity. Deposits are liabilities (the bank owes them back). Loans, reserves, securities, and buildings are assets. Equity is the owners' cushion.
• Banks create money when they lend. A $100,000 deposit lent and re-deposited becomes $200,000 of checking-deposit money — and the cycle continues until excess reserves run out.
• Banks destroy money when loans are repaid or deposits are withdrawn. Loan repayment shrinks deposit balances; the money supply contracts.
• Reserves come in two flavors: required reserves (held against checkable deposits, by law) and excess reserves (available for further lending). The required reserve ratio in the US was 10% for decades before being dropped to 0% in March 2020.

Mental model — the timeline of banking

click to zoom

Four thousand years of banking, told as institutional evolution.

Read it as: The institutional substrate keeps changing but the underlying problem stays the same — how to safely intermediate between savers and borrowers without periodic collapses of confidence. Every milestone is either a new way of doing the intermediation or a new defense against the failure modes it creates.

Mental model — how a deposit creates more money

click to zoom

Following $100,000 through a banking system with a 10% reserve requirement.

Read it as: Trace Alice’s $100,000 down the chain. Each bank keeps a fraction in reserve (10% in this example) and lends the rest. The borrower spends, and the recipient deposits the cash into another bank — which lends again. After many rounds the original $100,000 supports roughly $1,000,000 in deposit money. This is fractional-reserve banking. It’s also why a sudden contraction of lending crushes the money supply.

Mental model — a bank’s balance sheet

click to zoom

What a simplified bank balance sheet looks like and how the accounting identity holds.

Read it as: Your checking balance lives in the liability column — the bank owes you that money back on demand. The bank’s loans to other people live in the asset column. Equity is the gap between them, the cushion the owners have at risk. When loans go bad, the asset side shrinks and the equity cushion absorbs the loss — until it can’t, at which point the bank is insolvent.

Practical application

Read a bank’s earnings report intelligently

The three numbers that tell the story

When you read a bank’s quarterly report, the headline earnings number is almost never the most important one. Watch these three instead:

1. Net interest margin — the gap between the interest the bank earns on its loans and what it pays on its deposits. The bank’s core business is the spread.
2. Loan loss provisions — how much the bank set aside this quarter for loans it thinks will go bad. Rising provisions are an early warning of credit stress.
3. Tier 1 capital ratio — equity as a fraction of risk-weighted assets. The thinner this cushion, the closer the bank is to insolvency in a downturn.

Walk through your own deposit

1. 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).

2. 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%.

3. 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.

4. 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.

5. 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

Caution

The “money multiplier” textbook model in the diagram (a $100,000 deposit spawning $1,000,000 of deposit money) is a useful pedagogical fiction more than a literal description of how modern banks lend. In practice, banks lend first and then find the reserves — the constraint is capital and demand for credit, not the reserve ratio. The 2020 drop of the US reserve requirement to zero confirmed how thin the connection had become. But the basic fact — that lending creates deposit money and repayment destroys it — is exactly right, and the multiplier mental model is still the cleanest way to see it.

Related lessons

Related

Chapter 10: Inconvertible Fiat Explored M1 and M2 — the Fed's measures of the money supply that bank lending expands and contracts. Chapter 11: The Time Value of Money and Interest Rates Interest is what banks pay savers and charge borrowers — the spread is the bank's core business. Chapter 13: Banks as a System: Regulation and Deregulation How banks interact with each other, why bank runs happen, and the regulatory pendulum that has swung repeatedly since the 1860s. Concept: Fractional reserve banking The system in which banks hold only a fraction of deposits as reserves and lend out the rest, creating new deposit money in the process. Concept: Money supply The total stock of money in circulation and the role banks play in expanding and contracting it.