The Value of Money

The observation that we use money to buy things tells us more about the value of money. Economists often make a distinction between real and nominal values; this distinction can be applied to money as well. First, what is the nominal value of money? This is almost a trick question: we are asking, “How many dollars is a dollar bill worth?” The answer, which does not require a doctorate in economics, is that a dollar bill is worth $1.

Nominal variables—those measured in dollars or other currencies—can be converted into real variables—that is, those measured in units of real gross domestic product (real GDP). To convert a nominal variable to a real variable, we simply divide by the price level. For example, if your nominal wage is $20 per hour and the price level is $10 (meaning that a typical unit of real GDP costs this amount), then your real wage is 2 units of real GDP.

Exactly the same principle can be applied to money itself. The real value of a dollar is obtained by dividing one by the price level. Thus

Think of an economy in which real GDP is measured in pizzas and suppose the price level—the price of a pizza—is $10. Then the value of a dollar bill is 1/10 of a pizza.

Although $1 is always worth $1, you are not guaranteed that the dollar bill in your pocket will buy the same amount of goods and services from one day to the next. If your local café increases the price of a cookie from $1.00 to $1.25, then your $1 will no longer buy you a cookie; its value, measured in cookies, has declined. If the price level increases, then the real value of money decreases. For notes and coins to be a good store of value, it must be the case that prices are not increasing too quickly.We discuss this problem in more detail in Chapter 26 "Inflations Big and Small".

Using Money to Make Money: Arbitrage

An old joke has it that the secret to getting rich is very simple: buy at a low price and sell at a high price. So another use of your $100 would be to buy goods not to consume but to resell—a process known as arbitrageThe act of buying and then selling an asset to take advantage of profit opportunities..

Suppose you discovered that a particular model of digital camera could be bought much more cheaply in Minneapolis, Minnesota, than in Flagstaff, Arizona. Then you could purchase a large number of cameras in Minneapolis, load them into a suitcase, fly to Flagstaff, and sell them for a profit. If the gap in price were large enough to compensate for your time and travel costs, then this would be a money machine. By buying cameras at a low price and selling them at a high price, you could make as much profit as you wished.

This situation would not persist. You, and other entrepreneurs as well, would start to bid up the price of cameras in Minneapolis. Meanwhile, the increased supply of cameras in Flagstaff would cause prices there to decrease. Before too long, your money machine would have dried up: the gap between the Flagstaff price and the Minneapolis price would no longer justify the effort.

Arbitrage ensures that the prices of individual goods do not vary too much across different regions of the United States. Taken to its extreme, it would imply that the price level would be the same throughout the country. Economists call this idea the law of one priceDifferent prices for the same good or service will not persist because arbitrage eliminates such differences.. The law of one price says that different prices for the same good or service cannot persist because arbitrage eliminates such differences. Arbitrageurs would buy the good at the low price and sell it at the high price. Demand would increase in the market where the price was low, causing that price to increase. Supply would increase in the market where the price was high, causing that price to decrease. This process would continue until the prices were equalized across the two markets.

There are, of course, differences in the prices of individual goods and services in different states and different cities. These differences are primarily due to the fact that some items cannot be arbitraged. If cameras are cheaper in Minneapolis than in Flagstaff, then they can be bought and sold as we described. But if apartments in Flagstaff are cheaper than in Minneapolis, it isn’t possible to ship them across the country. Likewise services typically cannot be arbitraged. Thus we do not expect the law of one price to be literally true for every good and service. Nevertheless, the law of one price does lead us to expect that the overall price level will not differ too much in different parts of the country.

It can be difficult to apply the law of one price in practice because we have to be careful about what we mean by the “same” product. An apparently identical shirt at two different retailers might not qualify as the same—perhaps one retailer allows goods to be returned, while the other does not allow returns. Identical goods are not the same if they are in different places: a Toyota on a dealership lot in Kentucky is not the same as the identical model car on a lot in Pretoria, South Africa, and so on. In such situations, the law of one price tells us that we should not expect prices of goods to be “too different,” depending on the costs of transportation and the other costs of arbitrage.

We said earlier that money makes an economy more efficient because it makes transactions easier. Money makes arbitrage easier as well. Arbitrage would be a less certain way of making money in an economy with barter. First, the lack of a clear unit of account would make arbitrage opportunities less transparent. Second, the lack of a reliable medium of exchange would make arbitrage risky: the person in Flagstaff who wants to buy a digital camera from you might not have anything you want, so you might end up giving up something you own and not getting something you want in return.