Foundationsmacroeconomics
Money Supply: M1, M2, and How Money Is Measured
Overview
When economists say "the money supply," they do not mean a single number. Money exists on a spectrum of liquidity, from physical cash to savings deposits, and central banks track several aggregates to capture it. This lesson defines the standard measures — the monetary base, M1, and M2 — explains what is included at each level and why, and shows how the composition of money has shifted toward bank deposits and digital balances. You will also learn why the money supply matters for inflation and economic activity.
Learning objectives
- Define the monetary base (M0), M1, and M2 and list their components.
- Explain the liquidity spectrum from cash to time deposits.
- Interpret why M1 and M2 can move in different directions.
- Describe the link between money supply growth and inflation.
- Read a central bank money-supply release with understanding.
Money Is a Spectrum, Not a Single Number
A dollar bill, a checking-account balance, and a savings deposit all function as money, but they are not equally liquid — cash can be spent instantly anywhere, while a time deposit may carry withdrawal penalties. Because of this, economists measure money in nested aggregates, each broader than the last, capturing assets by how readily they serve as a medium of exchange. The narrowest measures track what can be spent immediately; broader ones add assets that can quickly be converted into spendable funds. Which aggregate matters most depends on the question: payments analysis leans on narrow money, while inflation analysis often watches broad money.
The Monetary Base (M0): The Foundation
The monetary base, sometimes called high-powered money or M0, consists of physical currency in circulation plus the reserves that commercial banks hold at the central bank. It is the narrowest aggregate and the only form of money the central bank creates directly. Every broader aggregate is ultimately built on this base through the banking system, which is why open market operations target it. Think of M0 as the raw material from which the rest of the money supply is manufactured.
Different countries label aggregates slightly differently, but the logic is universal: start with central-bank money, then add progressively less liquid bank liabilities.
M1: Money for Transactions
M1 is narrow money: currency in the hands of the public plus demand deposits (checking accounts) and other checkable deposits that can be spent immediately. In modern economies the deposit component dwarfs physical cash, since most transactions clear electronically. M1 answers the question "how much money is available for spending right now?" Because it tracks transaction balances so closely, M1 growth often moves with consumer spending and short-run economic activity.
M2: Adding Near-Money
M2 starts with everything in M1 and adds savings deposits, small time deposits, and retail money-market fund shares — assets that are not directly spendable but can be converted into spendable balances quickly and cheaply. These are called near-money: they serve the store-of-value function well and the medium-of-exchange function only indirectly. M2 is the headline aggregate most economists cite when discussing the money supply, because it captures the broad pool of liquid household wealth that can fuel spending. Rapid M2 growth relative to output growth is a classic warning sign of future inflation.
M0 is inside M1, and M1 is inside M2. Every component of a narrower aggregate is automatically part of every broader one — never double-count or treat them as separate piles.
Why the Composition Keeps Changing
A century ago, coins and notes dominated the money supply; today, bank deposits created through lending make up the overwhelming share in advanced economies. Financial innovation keeps redrawing the boundaries: money-market funds blurred the line between deposits and securities in the 1980s, and mobile money and stablecoins are doing it again now. Central banks periodically redefine the aggregates to keep up, which is why long historical comparisons need careful footnotes. The deeper lesson is that "money" is whatever the financial system has made liquid and generally acceptable at a given time.
Money Supply, Inflation, and Policy
The quantity theory of money offers a useful long-run intuition: if the money supply grows persistently faster than the economy's ability to produce goods, the price level tends to rise. This is why central banks watch the aggregates even when they set policy through interest rates rather than money targets. In the short run the link is loose — velocity, the rate at which money changes hands, fluctuates — but sustained rapid money growth has preceded nearly every major inflation. Understanding the aggregates is therefore the first step to understanding monetary policy itself.
Key points
- M0 (monetary base) = currency in circulation + bank reserves at the central bank.
- M1 = currency + demand/checkable deposits: money available for immediate spending.
- M2 = M1 + savings deposits, small time deposits, and retail money-market shares.
- Aggregates nest: everything in M0 is in M1, and everything in M1 is in M2.
- Most modern money is bank deposits created through lending, not physical cash.
- Sustained money growth faster than output growth is a classic inflation signal.
Common misconceptions
✓ Truth: Physical currency is a small fraction of broad money in modern economies. Most money is created by commercial banks when they make loans, which create matching deposits — the central bank influences this process but does not directly print the bulk of it.
✓ Truth: They can diverge: when households shift funds from checking into savings accounts, M1 falls while M2 is unchanged. Regulatory changes and new financial products routinely move money between aggregates without changing total liquidity much.
Practice questions
Q1. Which of the following is included in M1 but NOT part of the monetary base (M0)?
- Currency in circulation
- Bank reserves at the central bank
- Demand deposits at commercial banks
- Vault cash held by banks
Demand deposits are created by commercial banks, not the central bank, so they appear in M1 but not in M0. Currency in circulation and bank reserves (including vault cash) are central-bank money and belong to the base.
Q2. A household moves $5,000 from its checking account to its savings account. What happens to M1 and M2?
- Both M1 and M2 fall by $5,000
- M1 falls by $5,000; M2 is unchanged
- M1 is unchanged; M2 rises by $5,000
- Both M1 and M2 rise by $5,000
Checking deposits are in M1 while savings deposits are only in M2. Moving funds between them shrinks M1 by $5,000, but since both accounts sit inside M2, broad money does not change.
Q3. According to the quantity-theory intuition, sustained inflation is most likely when:
- Money supply growth persistently exceeds real output growth
- Velocity of money falls sharply
- The central bank raises reserve requirements
- Households shift deposits from M1 to M2
If money grows faster than the economy's capacity to produce goods and services for a sustained period, more money chases roughly the same output and the price level rises. The other options are either disinflationary or neutral for the total.
Q4. Why do economists say most modern money is 'created by banks'?
- Banks print their own banknotes
- Bank lending creates matching deposit balances that function as money
- Banks control the central bank's printing presses
- Bank vaults store all the economy's gold
When a bank approves a loan, it credits the borrower's deposit account — new purchasing power appears as a deposit liability. Physical printing is minor by comparison; the deposit expansion from lending is the main engine of broad money growth.
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Frequently asked questions
Is a savings account money?
It is near-money: included in M2 but not M1, because you cannot spend it directly at a checkout. Since it converts to spendable balances quickly, economists count it in broad money but not in narrow transaction money.
What is velocity and why does it matter?
Velocity is how many times the average unit of money is spent per year. If velocity falls — say, households hoard cash in a panic — the money supply can grow without inflation, which is why the money-inflation link is loose in the short run.
Do cryptocurrencies count in M1 or M2?
Standard official aggregates currently exclude crypto assets. They are generally too volatile and too rarely accepted as a medium of exchange to qualify, though central banks are studying how to treat them.
Why did M1 jump so much in 2020 in the US?
The Federal Reserve redefined M1 to include savings deposits, which had previously been only in M2. It was a definitional change reflecting that savings accounts had become highly liquid — a good reminder that aggregates are constructed, not discovered.