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

Money serves three basic functions. By definition, it is a medium of exchange. It also serves as a unit of account and as a store of value - as the "mack" did in Lompoc.

A Medium of Exchange

The exchange of goods and services in markets is among the most universal activities of human life. To facilitate these exchanges, people settle on something that will serve as a medium of exchange - they select something to be money.

We can understand the significance of a medium of exchange by considering its absence. Barter occurs when goods are exchanged directly for other goods. Because no one item serves as a medium of exchange in a barter economy, potential buyers must find things that individual sellers will accept. A buyer might find a seller who will trade a pair of shoes for two chickens. Another seller might be willing to provide a haircut in exchange for a garden hose. Suppose you were visiting a grocery store in a barter economy. You would need to load up a truckful of items the grocer might accept in exchange for groceries. That would be an uncertain affair; you could not know when you headed for the store which items the grocer might agree to trade. Indeed, the complexity - and cost - of a visit to a grocery store in a barter economy would be so great that there probably would not be any grocery stores! A moment's contemplation of the difficulty of life in a barter economy will demonstrate why human societies invariably select something - sometimes more than one thing - to serve as a medium of exchange, just as prisoners in federal penitentiaries accepted mackerel.

A Unit of Account

Ask someone in the United States what he or she paid for something, and that person will respond by quoting a price stated in dollars: "I paid $75 for this radio," or "I paid $15 for this pizza". People do not say, "I paid five pizzas for this radio". That statement might, of course, be literally true in the sense of the opportunity cost of the transaction, but we do not report prices that way for two reasons. One is that people do not arrive at places like Radio Shack with five pizzas and expect to purchase a radio. The other is that the information would not be very useful. Other people may not think of values in pizza terms, so they might not know what we meant. Instead, we report the value of things in terms of money.

Money serves as a unit of account, which is a consistent means of measuring the value of things. We use money in this fashion because it is also a medium of exchange. When we report the value of a good or service in units of money, we are reporting what another person is likely to have to pay to obtain that good or service.

A Store of Value

The third function of money is to serve as a store of value, that is, an item that holds value over time. Consider a $20 bill that you accidentally left in a coat pocket a year ago. When you find it, you will be pleased. That is because you know the bill still has value. Value has, in effect, been "stored" in that little piece of paper.

Money, of course, is not the only thing that stores value. Houses, office buildings, land, works of art, and many other commodities serve as a means of storing wealth and value. Money differs from these other stores of value by being readily exchangeable for other commodities. Its role as a medium of exchange makes it a convenient store of value.

Because money acts as a store of value, it can be used as a standard for future payments. When you borrow money, for example, you typically sign a contract pledging to make a series of future payments to settle the debt. These payments will be made using money, because money acts as a store of value.

Money is not a risk-free store of value, however. We saw in the chapter that introduced the concept of inflation that inflation reduces the value of money. In periods of rapid inflation, people may not want to rely on money as a store of value, and they may turn to commodities such as land or gold instead.