Definition, Measurement, and Functions of Money - AP Macroeconomics Study Guide

Core Concepts & Learning Goals

In economics, "money" is more than just the cash in your wallet. It is a specific type of asset that makes complex economies possible by simplifying transactions. Without a formal concept of money, we would rely on barter—trading goods for other goods—which is highly inefficient. This topic defines what qualifies as money, explores its three essential functions, and introduces the different ways economists measure the total amount of money in an economy.

After studying this topic, you should be able to define money, explain its functions, and calculate the two main measures of the money supply, M1 and M2, as well as the monetary base.

Key Concepts Breakdown

1. The Definition and Functions of Money

Money is any asset that is widely and readily accepted as a means of payment for goods and services. While we often think of currency, other assets like the funds in a checking account also function as money. For an asset to be considered money, it must effectively serve three distinct functions.

• Medium of Exchange: This is the most important function of money. It is an asset that buyers give to sellers when they want to purchase goods and services. Money eliminates the need for a "double coincidence of wants," where two parties in a barter system must each have something the other desires.

• Unit of Account: Money provides a common measure of value. It acts as a yardstick for posting prices and recording debts, allowing us to compare the value of different goods and services. For example, a car's price is stated in dollars, not in the number of pizzas it is worth.

• Store of Value: Money allows you to transfer purchasing power from the present to the future. You can hold money today and spend it tomorrow, next week, or next year. While other assets like stocks or real estate can also be a store of value, money is unique because of its liquidity, which is the ease with which an asset can be converted into the economy's medium of exchange.

2. Measuring the Money Supply: M1 and M2

The money supply is the total quantity of money available in the economy. It is measured using monetary aggregates, which are different groupings of financial assets based on their liquidity. The two most common monetary aggregates are M1 and M2.

• M1: This is the narrowest and most liquid measure of the money supply. It includes assets that are directly used for transactions.

  • Currency in circulation: Paper bills and coins in the hands of the non-bank public.

  • Demand deposits: Balances in bank accounts that depositors can access on demand by writing a check or using a debit card (i.e., checking accounts).

  The formula for M1 is:

  [ M1 = \text{Currency in circulation} + \text{Demand deposits} ]

• M2: This is a broader measure of the money supply. It includes all of M1 plus several types of assets that are not as liquid but can be easily converted into cash or checking deposits. These are often called "near-monies."

  • All of M1.

  • Savings deposits: Balances in savings accounts.

  • Small-denomination time deposits: Funds held in accounts like Certificates of Deposit (CDs) that have a specific maturity date.

  • Money market mutual funds: Funds that invest in short-term debt instruments.

  The formula for M2 is:

  [ M2 = M1 + \text{Savings deposits} + \text{Small time deposits} + \text{Money market funds} ]

3. The Monetary Base (M0 or MB)

The monetary base is a distinct measure from M1 and M2. It represents the total amount of a currency that is either in general circulation in the hands of the public or in the commercial bank deposits held in the central bank's reserves.

The components of the monetary base are:

• Currency in circulation: The same component found in M1.

• Bank reserves: Currency that banks hold in their vaults or as deposits at the central bank. These reserves are not available for the general public to spend and are therefore not included in M1 or M2.

The formula for the monetary base is:

[ \text{Monetary Base (MB)} = \text{Currency in circulation} + \text{Bank reserves} ]

Comparing Measures of Money

The key distinction between these measures is liquidity and who holds the asset. M1 is the most liquid. M2 is broader and less liquid. The monetary base includes reserves held by banks, which are not part of the money supply available to the public.

Step-by-Step Example

Let's calculate the monetary aggregates using a list of hypothetical financial assets for a small economy.

Given Data:

• Currency in circulation: $200 billion

• Demand deposits: $500 billion

• Bank reserves: $50 billion

• Savings deposits: $1,200 billion

• Small-denomination time deposits: $800 billion

Goal: Calculate M1, M2, and the Monetary Base (MB).

Step 1: Calculate M1

M1 consists of the most liquid assets: currency in circulation and demand deposits. We use the M1 formula.

• M1 = Currency in circulation + Demand deposits

• M1 = $200 billion + $500 billion

• M1 = $700 billion

Step 2: Calculate M2

M2 includes all of M1 plus near-monies like savings deposits and small time deposits. We use the M2 formula.

• M2 = M1 + Savings deposits + Small time deposits

• M2 = $700 billion + $1,200 billion + $800 billion

• M2 = $2,700 billion

Step 3: Calculate the Monetary Base (MB)

The monetary base includes currency in circulation and bank reserves. Note that we do not include demand deposits here, but we do include bank reserves, which were ignored for M1 and M2.

• MB = Currency in circulation + Bank reserves

• MB = $200 billion + $50 billion

• Monetary Base = $250 billion

This example highlights the specific components of each measure and shows how an asset like bank reserves can be part of the monetary base but not the money supply (M1/M2).

AP Exam Tips & Common Pitfalls

• [FRQ Task]: A common task on Free Response Questions is to provide a table of financial assets and ask you to calculate M1 and M2. Show your work clearly by writing out the formula and substituting the correct values.

• [MCQ Task]: Multiple-choice questions often test your understanding of which assets belong in which monetary aggregate. For example, a question might ask which of the following is included in M2 but not in M1 (e.g., a savings deposit).

• [Common Pitfall ①]: Confusing the money supply (M1/M2) with the monetary base. The most critical difference is bank reserves. Reserves are in the monetary base because the central bank created that currency, but they are not in M1 or M2 because that money is sitting in bank vaults, not circulating in the hands of the public.

• [Common Pitfall ②]: Forgetting that M1 is a component of M2. When calculating M2, do not just add up the "near-monies." You must start with the full value of M1 and then add the other components. A related error is including non-money financial assets like stocks and bonds in M1 or M2; these are not money because they are not a medium of exchange.

Key Vocabulary

• Money: Any asset that is widely accepted as a means of payment for goods and services.

• M1: The narrowest measure of the money supply, consisting of currency in circulation and demand deposits. It represents the most liquid forms of money.

• M2: A broader measure of the money supply that includes all of M1 plus less liquid assets such as savings deposits, small-denomination time deposits, and money market mutual funds.

• Monetary Base (MB): The sum of currency in circulation and bank reserves held at the central bank. It represents the total currency created by a central bank.

• Liquidity: The ease and speed with which an asset can be converted into a medium of exchange (like cash) without a significant loss of value.