ECON102: Principles of Macroeconomics (2021.A.01)

The total quantity of money in the economy at any one time is called the money supply. Economists measure the money supply because it affects economic activity. What should be included in the money supply? We want to include as part of the money supply those things that serve as media of exchange. However, the items that provide this function have varied over time.

Before 1980, the basic money supply was measured as the sum of currency in circulation, traveler's checks, and checkable deposits. Currency serves the medium-of-exchange function very nicely but denies people any interest earnings. (Checking accounts did not earn interest before 1980).

Over the last few decades, especially as a result of high interest rates and high inflation in the late 1970s, people sought and found ways of holding their financial assets in ways that earn interest and that can easily be converted to money. For example, it is now possible to transfer money from your savings account to your checking account using an automated teller machine (ATM), and then to withdraw cash from your checking account. Thus, many types of savings accounts are easily converted into currency.

Economists refer to the ease with which an asset can be converted into currency as the asset's liquidity. Currency itself is perfectly liquid; you can always change two $5 bills for a $10 bill. Checkable deposits are almost perfectly liquid; you can easily cash a check or visit an ATM. An office building, however, is highly illiquid. It can be converted to money only by selling it, a time-consuming and costly process.

As financial assets other than checkable deposits have become more liquid, economists have had to develop broader measures of money that would correspond to economic activity. In the United States, the final arbiter of what is and what is not measured as money is the Federal Reserve System. Because it is difficult to determine what (and what not) to measure as money, the Fed reports several different measures of money, including M1 and M2.

M1 is the narrowest of the Fed's money supply definitions. It includes currency in circulation, checkable deposits, and traveler's checks. M2 is a broader measure of the money supply than M1. It includes M1 and other deposits such as small savings accounts (less than $100,000), as well as accounts such as money market mutual funds (MMMFs) that place limits on the number or the amounts of the checks that can be written in a certain period.

M2 is sometimes called the broadly defined money supply, while M1 is the narrowly defined money supply. The assets in M1 may be regarded as perfectly liquid; the assets in M2 are highly liquid, but somewhat less liquid than the assets in M1. Even broader measures of the money supply include large time-deposits, money market mutual funds held by institutions, and other assets that are somewhat less liquid than those in M2. Figure 9.1 "The Two Ms: January 2012" shows the composition of M1 and M2 in October 2010.

Figure 9.1 The Two Ms: January 2012

M1, the narrowest definition of the money supply, includes assets that are perfectly liquid. M2 provides a broader measure of the money supply and includes somewhat less liquid assets. Amounts represent money supply data in billions of dollars for January 2012, seasonally adjusted.

Heads Up!

Credit cards are not money. A credit card identifies you as a person who has a special arrangement with the card issuer in which the issuer will lend you money and transfer the proceeds to another party whenever you want. Thus, if you present a MasterCard to a jeweler as payment for a $500 ring, the firm that issued you the card will lend you the $500 and send that money, less a service charge, to the jeweler. You, of course, will be required to repay the loan later. But a card that says you have such a relationship is not money, just as your debit card is not money.

With all the operational definitions of money available, which one should we use? Economists generally answer that question by asking another: Which measure of money is most closely related to real GDP and the price level? As that changes, so must the definition of money.

In 1980, the Fed decided that changes in the ways people were managing their money made M1 useless for policy choices. Indeed, the Fed now pays little attention to M2 either. It has largely given up tracking a particular measure of the money supply. The choice of what to measure as money remains the subject of continuing research and considerable debate.