Inflation — A Rising Money Supply Lifts All Prices

Inflation is always and everywhere a monetary phenomenon.
— Milton Friedman

3.1 What Is Inflation?

Imagine that you walk into your favorite coffee shop and discover that the price of a cup of coffee has increased from $4 to $5. Has inflation occurred?

Most people would answer "yes." After all, the price is higher than it was yesterday. Economists, however, would be more cautious. A higher price for one good does not necessarily mean the economy is experiencing inflation. To understand inflation, we must distinguish between a change in the price of a particular good and a change in the overall purchasing power of money.

Suppose that only the price of coffee rises because a poor harvest reduced the supply of coffee beans. Other prices in the economy remain unchanged. Consumers may choose to buy less coffee or switch to tea, but the purchasing power of money has changed very little. Now imagine a different situation in which the prices of coffee, gasoline, rent, groceries, clothing, restaurant meals, movie tickets, and thousands of other goods and services all rise over time. In this case, the purchasing power of money has declined. Each dollar now buys fewer goods and services than it did before. This is inflation.

Notice that this definition contains two important ideas. First, inflation refers to the overall price level rather than the price of a single good or service. Second, inflation is sustained. A one-time increase in prices is not the same thing as an ongoing inflationary process.

Inflation and Purchasing Power

The easiest way to understand inflation is to think about the purchasing power of money.

The purchasing power of money refers to the quantity of goods and services that a given amount of money can buy. When inflation occurs, each dollar buys fewer goods and services than it did previously. In other words, it is not that goods suddenly become more valuable—it is that money becomes less valuable relative to those goods.

Suppose you have a $20 bill.

If lunch costs $10, your $20 buys two lunches.

If inflation causes the price of lunch to rise to $20, your $20 now buys only one lunch.

Nothing about the paper bill has changed. It is still the same $20 bill. What has changed is its purchasing power.

Economists therefore often describe inflation as a decline in the value of money rather than simply an increase in prices. These are two ways of describing the same phenomenon.

Inflation Is Not the Same as Higher Prices

One of the most common misconceptions about inflation is that any increase in prices is inflation. This is incorrect.

Prices change constantly in a market economy. Some prices rise while others fall. New technologies make some products cheaper. Weather events make some agricultural products more expensive. Consumer preferences shift, changing the prices of countless goods and services.

These changes are examples of changes in relative prices. Relative prices help allocate scarce resources by signaling changes in supply and demand. They are an essential part of a well-functioning market economy.

Inflation is different. Inflation occurs when the purchasing power of money declines so that prices across much of the economy rise together over time.

For example, suppose a drought reduces the supply of oranges. Orange prices rise, but the prices of most other goods remain unchanged. Consumers may purchase fewer oranges and substitute other fruits instead. This is a change in a relative price, not inflation.

Now suppose that, over several years, the prices of oranges, apples, gasoline, rent, medical care, college tuition, clothing, restaurant meals, and thousands of other goods all rise persistently. This broad increase in prices reflects inflation because the purchasing power of money has declined.

Understanding this distinction is one of the most important ideas in macroeconomics.

Inflation, Deflation, and Disinflation

Economists use several related terms to describe changes in the overall price level.

Inflation means the overall price level is increasing.

Deflation means the overall price level is decreasing. During deflation, the purchasing power of money increases because each dollar can buy more goods and services than before.

Disinflation means that inflation is slowing. Prices are still rising, but they are rising at a slower rate than before.

For example:

Prices continue to rise each year, but the rate of increase is falling. This is disinflation, not deflation.

By contrast, if the inflation rate were (-2%), the economy would be experiencing deflation because the overall price level would be falling.

Why Economists Care About Inflation

Inflation affects nearly every economic decision.

Workers negotiate wages partly because they expect prices to change over time. Businesses consider inflation when deciding how much to charge for their products. Lenders and borrowers must think about inflation when agreeing on interest rates. Governments monitor inflation when designing monetary and fiscal policies. Investors consider inflation when deciding where to save and invest their money.

If inflation is low and predictable, households and businesses can plan for the future with greater confidence. When inflation becomes high or unpredictable, planning becomes more difficult. Individuals may spend more time protecting themselves from rising prices instead of focusing on productive economic activity.

For these reasons, understanding inflation is one of the central goals of macroeconomics.

3.2 Measuring Inflation

In the previous section, we learned that inflation is a sustained increase in the overall price level, or equivalently, a sustained decline in the purchasing power of money. This definition naturally raises an important question:

How do economists measure the overall price level?

Answering this question is more difficult than it might first appear. Every day, millions of transactions take place involving thousands of different goods and services. The prices of gasoline, groceries, rent, clothing, restaurant meals, airline tickets, medical care, and college tuition are all changing, often at different rates. Some prices increase, some decrease, and others remain unchanged.

Suppose the price of gasoline rises by 15%, while the price of televisions falls by 10%. Has inflation occurred?

The answer is not obvious. Looking at the price of only one or two goods tells us very little about what is happening to the purchasing power of money. Instead, economists need a way to summarize price movements across the entire economy.

Imagine walking through a grocery store with a shopping cart. Your cart contains bread, milk, eggs, fruit, meat, cereal, and vegetables. If the price of one item increases, your total grocery bill may not change very much. But if the prices of nearly everything in the cart increase, your total bill will almost certainly be higher.

Economists apply the same idea to the economy as a whole. Rather than tracking the price of a single product, they follow the cost of purchasing a representative collection of goods and services that households typically buy. By observing how the total cost of that collection changes over time, economists can estimate changes in the overall price level.

This representative collection is called a market basket.

Notice that the market basket does not include every good and service produced in the economy. Instead, it is designed to represent the spending patterns of the average household. If the cost of purchasing the same basket increases over time, this suggests that the purchasing power of money has fallen.

The Consumer Price Index

The most widely used measure of the overall price level is the Consumer Price Index, usually abbreviated as the CPI. The CPI is constructed by the Bureau of Labor Statistics (BLS), which regularly collects prices on tens of thousands of goods and services purchased by households throughout the United States.

The BLS begins by determining what a typical household buys. Through large national surveys, it estimates how households allocate their spending among categories such as food, housing, transportation, clothing, recreation, education, medical care, and many other goods and services. These spending patterns determine the composition of the market basket.

Each month, the BLS collects prices for the items in the basket from thousands of retail stores, service providers, landlords, hospitals, and other businesses across the country. It then compares the current cost of purchasing the basket with its cost during a selected base period.

If the basket costs more than it did previously, the CPI rises. If the basket costs less, the CPI falls. In this way, the CPI provides a summary measure of changes in consumer prices over time.

The CPI is reported as an index, not as a dollar amount. An index compares prices in one period with prices during a chosen base period. By convention, the base period is assigned a value of 100.

Suppose the cost of the market basket is exactly the same as it was during the base period. The CPI equals 100.

If the basket becomes 10% more expensive than it was in the base period, the CPI equals 110.

If the basket becomes 25% more expensive, the CPI equals 125.

Likewise, if the basket becomes 5% less expensive than during the base period, the CPI equals 95.

Because the CPI is an index rather than a dollar amount, economists can easily compare prices across different years without worrying about the actual cost of the basket.

Although the CPI is the most commonly reported measure of inflation, it is important to remember what it is measuring. The CPI does not measure the price of every good or service in the economy. Nor does it measure the cost of living for every individual household. Instead, it estimates how the prices paid by the average household change over time.

Comparing the CPI, GDP Deflator, and Producer Price Index

The Consumer Price Index is the most widely reported measure of inflation, but it is not the only price index economists use. Different price indexes are designed to answer different questions. Three of the most important are the Consumer Price Index (CPI), the GDP Deflator, and the Producer Price Index (PPI).

Although all three measure changes in prices, they differ in what prices they include, who purchases the goods and services, and how the market basket is constructed.

The Consumer Price Index (CPI)

As we have seen, the CPI measures the cost of purchasing a representative market basket of goods and services consumed by households. The basket is designed to reflect the spending patterns of a typical consumer and includes items such as food, housing, transportation, clothing, medical care, education, and recreation.

The CPI answers the following question:

How much has the cost of maintaining a typical household’s standard of living changed over time?

Because the CPI focuses on household purchases, it is the measure most commonly used when discussing the cost of living, wage adjustments, Social Security payments, and inflation experienced by consumers.

The GDP Deflator

The GDP Deflator measures the prices of all final goods and services produced domestically. Unlike the CPI, which follows a fixed market basket purchased by consumers, the GDP Deflator automatically adjusts as production changes over time.

Recall from Chapter 4 that the GDP Deflator is calculated as

$$GDP\ Deflator = \frac{Nominal\ GDP}{Real\ GDP} \times 100.$$

Because it is based on GDP, the GDP Deflator includes goods and services purchased by households, businesses, governments, and foreign buyers, provided they are produced within the country.

It therefore answers a different question:

How have the prices of all domestically produced final goods and services changed over time?

One important consequence is that imported goods affect the CPI but do not directly affect the GDP Deflator. For example, if the price of imported smartphones increases, consumers pay higher prices, so the CPI increases. However, because those smartphones were produced outside the country, they are not included in GDP and therefore do not directly affect the GDP Deflator.

Likewise, prices of domestically produced capital equipment purchased by businesses are included in the GDP Deflator but are not part of the CPI because households do not typically purchase industrial machinery.

The Producer Price Index (PPI)

The Producer Price Index (PPI) measures changes in the prices received by producers for the goods and services they sell. Rather than focusing on consumers, the PPI looks at prices earlier in the production process.

For example, the PPI tracks prices received by:

• farmers selling wheat,

• steel producers selling steel,

• oil companies selling crude petroleum,

• manufacturers selling automobiles,

• wholesalers selling products to retailers.

The PPI answers the question:

How are prices changing for businesses producing goods and services?

Because producers often experience cost increases before consumers do, economists sometimes view the PPI as an indicator of future inflationary pressures. For example, if steel producers begin charging significantly higher prices, automobile manufacturers may eventually face higher production costs. If those higher costs are passed on to consumers, automobile prices may later increase, contributing to higher CPI inflation.

However, this relationship is not automatic. Businesses do not always pass higher costs on to consumers. Competitive pressures, productivity improvements, or lower profit margins may absorb some or all of the increase.

Comparing the Three Price Indexes

Although the CPI, GDP Deflator, and PPI all measure price changes, each serves a different purpose.

No single price index is “better” than the others. Instead, each provides different information.

The CPI is most useful when economists want to understand how inflation affects households.

The GDP Deflator is most useful when studying overall economic production because it covers everything included in GDP.

The PPI is useful for understanding cost pressures facing businesses and for analyzing price changes earlier in the production process.

By examining all three indexes together, economists gain a more complete picture of inflation throughout the economy.

Limitations of Price Indexes

Price indexes such as the Consumer Price Index (CPI), the GDP Deflator, and the Producer Price Index (PPI) are among the most important tools used by economists. They provide valuable information about changes in prices and allow economists to measure inflation over time. However, like all economic statistics, they are estimates rather than perfect measures of reality.

No single price index can capture the experiences of every household or business. People’s spending habits differ, new products are introduced, existing products improve in quality, and consumers adjust their purchases as relative prices change. These factors create several important limitations that economists must keep in mind when interpreting measures of inflation.

A Representative Household Is Not Every Household

The Consumer Price Index is based on the spending patterns of a typical household. In reality, no household is truly typical.

A retired couple may spend a much larger share of its income on health care than a college student. A family with young children may spend heavily on childcare and education, while a single professional may spend much more on travel and entertainment.

Because households purchase different combinations of goods and services, they may experience different rates of inflation even when the national CPI reports a single inflation rate.

For example, suppose gasoline prices rise sharply while food and housing prices remain relatively stable. A family that commutes long distances every day may experience a much larger increase in its cost of living than a family that rarely drives.

The CPI therefore measures the inflation experienced by the average household—not by every household.

Substitution Bias

One limitation of the CPI is known as substitution bias. The CPI measures the cost of purchasing a fixed market basket. In reality, however, consumers often change what they buy when relative prices change.

Suppose the price of beef rises substantially while the price of chicken remains unchanged. Many households may respond by purchasing more chicken and less beef. Their actual cost of maintaining a similar standard of living may therefore increase by less than the CPI suggests.

Because the CPI follows a predetermined basket, it does not immediately account for these substitutions. As a result, it may somewhat overstate increases in the cost of living.

New Goods

Markets continually introduce new products. Smartphones, streaming services, electric vehicles, wearable technology, and countless other products did not exist—or were very different—a generation ago.

New goods often improve consumers’ well-being by providing more choices, better quality, or lower prices. However, a fixed market basket cannot immediately include products that did not previously exist.

As a result, the CPI may temporarily miss some of the benefits that consumers receive from innovation until the market basket is updated.

Quality Improvements

Many products improve over time.

A laptop purchased today is much more powerful than one purchased ten years ago. Automobiles often become safer and more fuel efficient. Medical treatments become more effective. Household appliances consume less energy.

When the price of a product increases, part of that increase may simply reflect higher quality rather than inflation.

Suppose a smartphone costs $1,000 today instead of $800 five years ago. At first glance, the price appears to have increased by 25%. But today’s smartphone may include a faster processor, a better camera, more storage, longer battery life, and new software features.

Economists therefore face the difficult task of separating price increases caused by inflation from price increases caused by improvements in quality.

Government statistical agencies devote substantial effort to making these quality adjustments, but they are not always straightforward.

Changing Spending Patterns

Consumer preferences evolve over time.

Households today spend differently than households did twenty or thirty years ago. New technologies, changing lifestyles, demographic shifts, and economic conditions continually alter spending patterns.

For this reason, the Bureau of Labor Statistics periodically updates the CPI market basket to better reflect current consumer behavior. Without these updates, the CPI would become less representative of the average household.

Even with regular updates, however, no market basket can perfectly reflect the purchasing decisions of millions of different households.

Interpreting Inflation Measures Carefully

These limitations do not mean that price indexes are unreliable. On the contrary, the CPI, GDP Deflator, and PPI are among the most carefully constructed economic statistics available.

Instead, these limitations remind us that inflation measures are estimates designed to summarize the behavior of a very large and diverse economy. Like averages discussed in Chapter 4, they provide valuable information but should not be interpreted too literally.

Economists therefore often examine multiple price indexes together and consider additional information before drawing conclusions about inflationary pressures in the economy.

3.3 The Quantity Theory of Money

One of the most important relationships in macroeconomics is the Equation of Exchange. This equation summarizes the relationship between the money supply, spending in the economy, the overall price level, and real economic output.

The Equation of Exchange is written as

$$MV = PY$$

This equation is the foundation of the Quantity Theory of Money, which we will develop more fully in the next section. For now, our goal is simply to understand what each variable represents and how to use the equation.

Notice that the left-hand side of the equation and the right-hand side measure the same thing from different perspectives.

The left-hand side, (MV), measures the total amount of spending in the economy.

The right-hand side, (PY), measures the dollar value of all final goods and services produced. Since (P) is the average price level and (Y) is real output, their product is nominal GDP.

Therefore,

$$MV = Nominal\ GDP$$

The Equation of Exchange tells us that total spending in the economy equals the total value of production.

Understanding the Variables

Each variable in the equation has a specific meaning.

Money Supply (M)

The variable M represents the quantity of money available in the economy. Depending on the context, economists may measure the money supply using different definitions such as M1 or M2, we will address the definitions of the money supply formally in Chapter 10. Throughout this chapter, we simply think of M as the total amount of money available for spending.

Velocity of Money (V)

The variable V represents the velocity of money. Velocity measures the average number of times each dollar is used to purchase final goods and services during a given period.

For example, if the average dollar is spent five times during a year, then

$$V = 5.$$

A higher velocity means that money circulates through the economy more rapidly.

Price Level (P)

The variable P represents the overall price level in the economy. Rather than measuring the price of a single good, P summarizes prices across many goods and services using measures such as the Consumer Price Index or the GDP Deflator.

Real Output (Y)

The variable Y represents real output, or real GDP. It measures the quantity of final goods and services produced after removing the effects of inflation.

Unlike PY, which measures production in current dollars, Y measures real production.

The Equation of Exchange in Growth Rates

Although the Equation of Exchange is written as

$$MV = PY,$$

macroeconomists often use a slightly different version that focuses on the percentage change of each variable over time. Expressing the equation in growth rates makes it much easier to analyze inflation and economic growth.

The growth-rate form of the Equation of Exchange is

$$\%\Delta M + \%\Delta V \ = \ \%\Delta P + \%\Delta Y.$$

This equation says that the growth rate of the money supply plus the growth rate of velocity equals the inflation rate plus the growth rate of real output.

Notice that each variable is now measured as a percentage change rather than as a level. This allows economists to study how changes in money, velocity, prices, and production are related over time.

Throughout the remainder of this chapter, we will primarily use this growth-rate version because it makes the relationship between money growth and inflation much easier to understand.

Examples

Suppose an economy experiences the following changes during one year:

• Money supply grows by 6%.

• Velocity of money does not change.

• Real GDP grows by 2%.

Using the growth-rate form of the Equation of Exchange, $$\%\Delta M + \%\Delta V \ = \ \%\Delta P + \%\Delta Y.$$ substitute the known values:

$$6\% + 0\% \ = \ \%\Delta P + 2\%$$

Now solve for the inflation rate:

$$\%\Delta P \ = 6\% - 2\% = 4\%.$$

The economy therefore experiences an inflation rate of 4%.

Suppose the inflation rate is 5%, real GDP grows by 3%, and the velocity of money decreases by 1%.

What must have been the growth rate of the money supply?

Using $$\%\Delta M + \%\Delta V \ = \ \%\Delta P + \%\Delta Y.$$ substitute the known values: $$\%\Delta M+(-1\%) \ = \ 5\%+3\%.$$

Simplifying,

$$\%\Delta M-1\%=8\%.$$

Therefore, $$\%\Delta M=9\%.$$

The money supply must have increased by 9%.

In the next section, we will use this simple relationship to explain one of the most important ideas in macroeconomics: why Milton Friedman argued that inflation is “always and everywhere a monetary phenomenon.” Rather than simply memorizing that statement, you will use the Equation of Exchange to understand the economic logic behind it.

3.4 Inflation Is Always and Everywhere a Monetary Phenomenon

In the previous section, we introduced the Equation of Exchange and showed that it can be written in terms of growth rates as $$\%\Delta M + \%\Delta V \ = \ \%\Delta P + \%\Delta Y.$$ This equation relates four important macroeconomic variables:

• the growth rate of the money supply,

• the growth rate of the velocity of money,

• the inflation rate, and

• the growth rate of real GDP.

By itself, this equation is simply an accounting identity. It tells us that total spending in the economy must equal the value of total production, but it does not explain why inflation occurs.

To understand inflation, economists must make one additional observation about how these variables behave over time.

One of the most influential economists of the twentieth century, Milton Friedman, argued that over long periods of time, inflation is primarily determined by the growth of the money supply. He summarized this idea with one of the most famous statements in economics:

“Inflation is always and everywhere a monetary phenomenon.”

At first glance, this statement may seem surprising. Prices change for many reasons. Weather affects food prices. Wars disrupt energy markets. New technologies lower the prices of some products while increasing demand for others. How, then, could Friedman argue that inflation is fundamentally monetary?

The answer begins by examining the role of the velocity of money.

Assuming Velocity Is Relatively Stable

Recall that the variable V represents the velocity of money—the average number of times each dollar is used to purchase final goods and services during a given period.

In reality, velocity does change from year to year. Changes in payment technologies, interest rates, financial innovation, consumer confidence, and banking behavior can all influence how rapidly money circulates through the economy.

However, economists have found that over long periods of time, changes in velocity are generally much smaller than changes in the money supply or the price level. While velocity may fluctuate in the short run, it tends to be relatively stable over longer horizons.

For this reason, economists often make a simplifying assumption:

$$\%\Delta V \approx 0.$$

This assumption does not mean that velocity never changes. Instead, it means that changes in velocity are small enough that they are unlikely to be the primary source of sustained inflation over many years.

Making this assumption greatly simplifies the Equation of Exchange and allows us to focus on the relationship between money growth, real economic growth, and inflation.

Deriving the Quantity Theory of Money

Begin with the growth-rate form of the Equation of Exchange:

$$\%\Delta M + \%\Delta V \ = \ \%\Delta P + \%\Delta Y.$$

If velocity is approximately constant, then

$$\%\Delta V \approx 0.$$

Substituting this assumption into the Equation of Exchange gives

$$\%\Delta M \ = \ \%\Delta P + \%\Delta Y.$$

Since the growth rate of the price level is simply the inflation rate, we can rewrite the equation as

$$\%\Delta M \ = \ Inflation + Real\ GDP\ Growth.$$

This relationship is the heart of the Quantity Theory of Money.

It tells us that the growth rate of the money supply must ultimately be reflected in one of two places:

1. higher real production, or

2. higher prices.

If the economy is capable of producing more goods and services, some of the increase in the money supply can support greater real output. But if the money supply grows faster than the economy’s ability to produce goods and services, the remaining increase must appear as inflation. Further, it is often said that “inflation is caused by too many dollars chasing too few goods.” The relationship between $\%\Delta M$ and $\%\Delta P + \%\Delta Y$ when $\%\Delta M$ increases faster than $\%\Delta Y$ perfectly follows this statement as well.

This insight provides the foundation for understanding why economists often describe persistent inflation as a monetary phenomenon.

Notice that this equation does not yet tell us how much of money growth becomes inflation or how much becomes real economic growth. That depends on how rapidly the economy is able to expand its production of goods and services.

In the remainder of this section, we will use this simple relationship to examine several economies with different rates of money growth and real GDP growth. By working through these examples, you will see why Friedman concluded that persistent inflation occurs whenever the money supply grows faster than the economy’s productive capacity.

Historical Evidence: Hyperinflation and the Money Supply

Economic theories are valuable only if they help explain what we observe in the real world. One of the strongest pieces of evidence supporting the Quantity Theory of Money comes from episodes of hyperinflation. Hyperinflation refers to an extremely rapid increase in the overall price level, often exceeding 50% per month. During these episodes, money loses its purchasing power so quickly that people rush to spend it almost immediately after receiving it.

Although every historical episode has its own political and economic circumstances, hyperinflations share one striking characteristic: governments financed large and persistent budget deficits by creating enormous quantities of new money. As the money supply expanded far more rapidly than the production of goods and services, prices rose dramatically.

Germany: The Weimar Hyperinflation

One of the best-known examples occurred in Germany following the First World War. The German government faced enormous financial obligations, including war debts and reparations imposed by the Treaty of Versailles. Rather than raising enough taxes or borrowing sufficient funds, the government increasingly financed its spending by printing money.

As the quantity of money expanded, prices began rising rapidly. By 1923, inflation had become hyperinflation. Prices sometimes doubled within a matter of days. Workers were often paid several times each day so they could spend their wages before prices increased again. Savings accumulated over a lifetime became nearly worthless, and many ordinary transactions became extremely difficult because money was losing value so quickly.

Although the immediate causes of Germany’s fiscal problems were unique to the postwar period, the mechanism behind the hyperinflation was straightforward. The supply of money grew far more rapidly than the economy’s ability to produce goods and services, causing the purchasing power of money to collapse.

Zimbabwe

Zimbabwe experienced another dramatic hyperinflation during the 2000s. Political instability, declining agricultural production, and falling economic output placed severe pressure on government finances. Rather than reducing spending or raising sufficient tax revenue, the government increasingly relied on its central bank to finance expenditures by creating new money.

As confidence in the currency deteriorated, the government responded by printing even more money. This only accelerated inflation. Prices began rising at astonishing rates, eventually reaching billions of percent per year according to many estimates. Currency notes with denominations of millions, billions, and even trillions of Zimbabwean dollars were issued, yet they often purchased only a few everyday items.

Eventually, the Zimbabwean dollar became essentially unusable, and the country abandoned its currency in favor of foreign currencies for many transactions.

Venezuela

More recently, Venezuela experienced a prolonged period of extremely high inflation beginning in the middle of the 2010s. The country faced declining oil revenues, falling economic production, and large government budget deficits. Rather than financing these deficits through taxation or sustainable borrowing, the government increasingly relied on monetary expansion.

As the money supply grew rapidly while real output declined, prices accelerated dramatically. The purchasing power of the Venezuelan bolívar fell sharply, making it increasingly difficult for households to purchase basic necessities. Many people sought to hold foreign currencies or other assets instead of domestic money because they expected the bolívar to continue losing value.

Unlike Germany and Zimbabwe, Venezuela’s inflation developed over several years rather than exploding almost overnight. Nevertheless, the underlying pattern was similar: persistent growth in the money supply greatly exceeded growth in real output.

What These Episodes Have in Common

Germany, Zimbabwe, and Venezuela differed in many important respects. They occurred in different centuries, on different continents, under different political systems, and in response to different economic crises.

Yet all three episodes shared a common pattern.

1. Governments experienced severe fiscal problems.

2. Governments financed spending by creating large amounts of new money.

3. The money supply grew much faster than real economic output.

4. The purchasing power of money declined dramatically.

5. Prices rose rapidly throughout the economy.

These episodes do not suggest that every increase in the money supply immediately produces hyperinflation. Modern central banks routinely increase the money supply to accommodate normal economic growth and changes in the demand for money.

The important lesson is different. When the money supply persistently grows much faster than an economy’s ability to produce goods and services, the historical record shows that sustained inflation—and in extreme cases, hyperinflation—has almost always followed.

For Milton Friedman, these historical experiences provided compelling evidence for his famous conclusion that inflation is fundamentally a monetary phenomenon. While wars, natural disasters, supply disruptions, and political instability can all affect individual prices or temporarily influence inflation, none of these factors alone can explain the sustained, economy-wide increases in prices observed during episodes of hyperinflation. In each case, rapid monetary expansion was the common element.

3.5 Common Misconceptions About Inflation

By now, we have developed a simple but powerful explanation of inflation. The Quantity Theory of Money shows that when the money supply grows persistently faster than an economy’s ability to produce goods and services, the purchasing power of money declines and the overall price level rises.

Despite this straightforward relationship, inflation is one of the most misunderstood topics in economics. News reports, political debates, and everyday conversations often attribute inflation to many different causes. Some of these explanations contain an element of truth, while others confuse changes in individual prices with sustained inflation.

The purpose of this section is to examine several common misconceptions and evaluate them using the economic principles developed in this chapter.

Misconception 1: Inflation Is Caused by Greedy Businesses

A common claim is that inflation occurs because businesses become greedier and decide to charge higher prices.

At first glance, this explanation may seem reasonable. If firms raise prices, consumers must pay more, so prices increase.

The problem with this explanation is that it does not answer a fundamental question:

Why didn’t businesses raise all of their prices last year? Or five years ago?

Businesses have always preferred higher profits. The desire to earn profits is not new, nor does it suddenly appear during periods of inflation.

In competitive markets, firms cannot simply charge any price they wish. Consumers must have enough purchasing power to pay those higher prices. If one restaurant suddenly doubles its prices while competitors do not, many customers will simply eat somewhere else.

For prices throughout the economy to continue rising year after year, consumers must have sufficient money to purchase goods and services at those higher prices. This is why economists distinguish between a firm’s desire to raise prices and the economy’s ability to sustain higher overall prices.

Greed may influence the pricing decisions of individual firms, but it does not explain why the overall purchasing power of money declines across an entire economy.

Moreover, if firms decided to be altruistic and decline to raise prices when there is more money in the economy, the inflation rate would still increase because entrepreneurial individuals would use their larger supply of dollar bills to buy large stocks of goods to resell at higher prices. This is possible because many other individuals will now have more dollar bills in their pockets as a result of the increase in the money supply. This is a simple application of the fact that consumers drive higher prices, not businesses.

Misconception 2: Inflation Is Caused by Rising Oil Prices

Oil prices affect many industries because petroleum is used to produce gasoline, diesel fuel, plastics, fertilizers, and countless other products.

When oil prices rise sharply, transportation becomes more expensive, shipping costs increase, and some goods become more costly to produce.

These effects are real.

However, higher oil prices alone cannot explain persistent inflation.

Suppose oil prices double while the money supply remains unchanged. Consumers now spend more of their income on gasoline and energy, leaving less income available to purchase other goods and services. Some prices may rise, while others may fall as consumer spending shifts.

The result is primarily a change in relative prices, not necessarily a sustained increase in the overall price level.

Oil shocks can temporarily increase measured inflation, but they do not explain why prices continue rising year after year.

Misconception 3: Supply Shortages Cause Inflation

Supply disruptions became a common topic during the COVID-19 pandemic. Shortages of computer chips, automobiles, building materials, and shipping capacity contributed to higher prices for many products.

These shortages certainly affected individual markets.

But shortages alone do not create persistent inflation.

If the supply of automobiles falls, automobile prices rise. Consumers may postpone purchases or spend less on other goods. Resources are reallocated throughout the economy as relative prices change.

Without sustained monetary expansion, supply shortages redistribute spending rather than continually increasing the overall price level.

This distinction is one of the most important lessons in macroeconomics:

Supply shocks change relative prices.

Persistent inflation changes the purchasing power of money.

Misconception 4: Printing Money Makes Society Richer

Suppose the government printed enough money to give every household an additional $100,000.

Would society become richer?

The answer is no.

Printing additional money creates more dollars, but it does not create more houses, automobiles, computers, food, factories, machinery, or workers.

Real wealth comes from producing goods and services.

Money is simply the medium used to exchange them.

If the quantity of money increases while the quantity of goods and services remains unchanged, households have more dollars chasing the same amount of production. As we have seen through the Quantity Theory of Money, the likely result is a higher price level rather than greater real wealth.

This misconception is particularly pernicious, as evidenced by the fact New York State sent “inflation relief checks” for $300 to taxpayers in 2025. (INCLUDE PHOTO OF THE CHECK HERE)

Misconception 5: Inflation Is Good Because Prices Are Higher

Some people assume that rising prices automatically make society wealthier because businesses receive more revenue.

This reasoning confuses nominal values with real values.

Suppose every price and every wage doubled overnight.

Would society have twice as many houses?

Twice as much food?

Twice as many doctors?

Twice as many automobiles?

Of course not.

Everyone would receive more dollars, but each dollar would purchase less.

Real production—and therefore real wealth—would be unchanged.

Economists therefore distinguish carefully between nominal increases in prices and real increases in production. Inflation changes the value of money, not the economy’s productive capacity.

3.6 The Costs of Inflation

Inflation is a sustained increase in the overall price level, or equivalently, a sustained decline in the purchasing power of money. But why should we care if prices are rising? The answer is more subtle than simply saying that “things cost more.”

If all prices and incomes increased at exactly the same rate, and everyone knew in advance precisely how much inflation would occur, many of the effects of inflation would be relatively small. A worker whose wage doubled while every price also doubled would have twice as many dollars but approximately the same purchasing power.

The most important costs of inflation arise because inflation complicates economic decisions, changes relative prices, interacts with contracts written in dollars, and is often difficult to predict. These problems become especially significant when inflation is high, volatile, or unexpected.

Menu Costs

Inflation forces businesses to change prices more frequently. Changing a price may sound inexpensive, but businesses can incur real costs when they update prices. Historically, restaurants had to print new menus whenever prices changed significantly. Economists therefore refer to these expenses as menu costs.

Modern menu costs extend far beyond printing physical menus. Businesses may need to:

• update websites and computer systems,

• change price labels,

• revise catalogs,

• renegotiate contracts,

• notify customers,

• reconsider pricing strategies.

Each individual adjustment may be inexpensive, but repeated across millions of businesses, these costs consume resources that could otherwise be used productively. The higher and more unpredictable inflation becomes, the more frequently businesses may need to reconsider their prices.

Price Confusion

One of the most important functions of prices is to communicate information. Recall that a price tells consumers and producers something about the relative scarcity and value of a good. Inflation makes these signals more difficult to interpret.

Suppose the price of a restaurant meal rises by 8%. Does this mean:

• consumers have become more willing to pay for restaurant meals,

• food has become relatively scarce,

• labor costs in restaurants have increased,

• or the overall price level has simply increased by approximately 8%?

During periods of stable prices, changes in individual prices provide relatively clear information about changes in particular markets. During periods of rapid inflation, businesses and consumers must distinguish between changes in relative prices and changes in the overall price level.

This confusion can lead to mistakes. Businesses may incorrectly interpret higher nominal prices as evidence of stronger demand and expand production when the relative demand for their product has not actually increased. Consumers may similarly have difficulty determining whether one product has genuinely become more expensive relative to alternatives. Inflation therefore reduces the informational clarity of the price system.

Money Illusion

Inflation can also make it difficult to distinguish between nominal and real changes. This problem is called money illusion.

Suppose your salary increases from: $$\$50{,}000$$ to: $$\$52{,}500.$$ Your nominal wage increased by: $$5\%.$$ You might initially conclude that you are better off. But suppose inflation was: $$7\%.$$ Prices increased faster than your income. Your purchasing power actually declined. Approximately: $$Real\ Wage\ Growth \approx Nominal\ Wage\ Growth-Inflation.$$ Therefore: $$Real\ Wage\ Growth \approx 5\%-7\% = -2\%.$$ Your paycheck contains more dollars, but those dollars purchase fewer goods and services than before.

Money illusion can affect discussions of wages, investment returns, profits, and many other economic variables. Whenever inflation is present, economists distinguish carefully between nominal and real values.

Inflation Redistributes Wealth

Unexpected inflation can create winners and losers even when total real resources in the economy have not changed. One of the clearest examples involves borrowers and lenders.

Suppose you borrow: $$\$100{,}000$$ at a fixed interest rate of: $$4\%.$$ The loan contract specifies repayment in dollars. What matters for the lender, however, is not simply how many dollars are repaid. What matters is the purchasing power of those dollars.

Suppose both borrower and lender expected inflation of 2%, but inflation unexpectedly rises to 8%. The dollars used to repay the loan are now worth less than expected. The borrower benefits because the debt is repaid with dollars having lower purchasing power. The lender loses because the money received purchases fewer goods and services than anticipated.

This distinction is important because anticipated inflation can often be incorporated into interest rates and contracts. If lenders expect high inflation, they can demand higher nominal interest rates as compensation. Unexpected inflation is more disruptive because existing contracts were negotiated using different expectations.

The Real Interest Rate

The relationship between inflation, borrowers, and lenders can be understood using the real interest rate. Approximately: $$Real\ Interest\ Rate = Nominal\ Interest\ Rate - Inflation.$$

Suppose a lender receives a nominal interest rate of: $$6\%.$$ If inflation is: $$2\%,$$ the approximate real return is: $$6\%-2\%=4\%.$$ But if inflation unexpectedly becomes: $$7\%,$$ the real return becomes approximately: $$6\%-7\%=-1\%.$$ The lender receives more dollars than were originally lent but loses purchasing power. This is why unexpected inflation can create substantial transfers of real wealth.

Inflation Inertia

Once inflation becomes established, it can become difficult to reduce quickly. Workers and businesses form expectations about future inflation and incorporate those expectations into contracts. Suppose inflation has remained near 8% for several years. Workers may reasonably expect prices to continue increasing rapidly and therefore negotiate wage increases of approximately 8%. Businesses anticipate higher wage and input costs and incorporate those increases into their pricing decisions. Inflation expectations can therefore become embedded in economic behavior. Economists sometimes refer to this persistence as inflation inertia.

Inflation inertia does not mean expectations create inflation independently of monetary conditions. Rather, expectations influence how quickly wages and prices adjust when policymakers attempt to reduce inflation. If workers expect 8% inflation, wage contracts may continue reflecting those expectations even after monetary conditions begin changing. This can make reducing inflation economically painful in the short run.

Why Stopping Inflation Can Be Painful

Suppose an economy has experienced high inflation for several years. Workers expect high inflation. Businesses expect their costs to continue increasing. Contracts have been negotiated around those expectations.

Now suppose monetary authorities reduce money growth in an attempt to lower inflation. Nominal spending growth slows. However, wages and other production costs may not immediately adjust because they were negotiated under expectations of higher inflation. Businesses can therefore experience slower revenue growth while their costs remain elevated. They may respond by:

• reducing production,

• reducing hiring,

• cutting worker hours,

• laying off employees.

The economy may experience slower real GDP growth and higher unemployment while inflation expectations gradually adjust downward.

This creates an important lesson for monetary policy. Preventing high inflation from becoming established can be considerably less costly than eliminating it after households and businesses have incorporated high inflation into their expectations.

Predictable Inflation Versus Unexpected Inflation

Many of the costs discussed in this section depend on whether inflation is predictable. If everyone knows that inflation will be exactly 2%:

• workers can incorporate it into wage negotiations,

• lenders can incorporate it into interest rates,

• businesses can anticipate changes in costs,

• households can make better long-term plans.

Inflation still creates some costs, including menu costs and complications involving nominal prices. But unexpected and volatile inflation creates substantially greater problems.

This is one reason economists and central banks place considerable value on price stability: keeping inflation sufficiently low and predictable that it does not significantly interfere with economic decision-making.

Chapter Summary

Inflation is one of the most important topics in macroeconomics because it affects every household, business, and government. Inflation changes the purchasing power of money, influences wages and interest rates, affects investment decisions, and plays a central role in monetary policy. Understanding why inflation occurs begins with understanding what inflation actually is.

Section 3.1 defined inflation as a sustained increase in the overall price level, or equivalently, a sustained decline in the purchasing power of money. This distinction is important because inflation refers to changes in the prices of goods and services throughout the economy rather than changes in the price of a single product. Rising gasoline prices, higher housing costs, or temporary food shortages may change individual prices without producing sustained inflation.

Section 3.2 explained how economists measure inflation using price indexes. The Consumer Price Index (CPI) measures the cost of purchasing a representative market basket of goods and services consumed by households. The CPI is the most commonly reported measure of inflation because it reflects changes in the prices consumers pay. The chapter also introduced the GDP Deflator, which measures prices for all final goods and services produced domestically, and the Producer Price Index (PPI), which measures prices received by producers. Although each index measures inflation differently, together they provide a more complete picture of price changes throughout the economy.

The chapter also discussed the limitations of price indexes. Because households purchase different goods and services, no single price index perfectly represents everyone’s experience with inflation. Economists must also account for substitution between goods, improvements in product quality, the introduction of new products, and changing spending patterns. As a result, price indexes should be viewed as carefully constructed estimates rather than perfect measures of changes in the cost of living.

Section 3.3 introduced the Quantity Theory of Money through the Equation of Exchange:

$$MV = PY.$$

Students learned that the equation is often written in growth-rate form:

$$\%\Delta M + \%\Delta V = \%\Delta P + \%\Delta Y.$$

This equation relates growth in the money supply, changes in the velocity of money, inflation, and real GDP growth. At this stage, the focus was on understanding the variables and learning how to solve simple problems using the equation.

Section 3.4 provided the economic interpretation of the Equation of Exchange. Assuming that the velocity of money is relatively stable over long periods, the Quantity Theory simplifies to

$$\%\Delta M = Inflation + Real\ GDP\ Growth.$$

This relationship explains why persistent inflation occurs when the money supply grows faster than the economy’s ability to produce goods and services. If real GDP grows, some money growth can support additional production. However, when money growth consistently exceeds real GDP growth, the remaining increase appears as inflation.

Historical episodes of hyperinflation provide powerful evidence supporting this conclusion. Germany during the Weimar Republic, Zimbabwe during the 2000s, and Venezuela during the 2010s all experienced rapid and persistent monetary expansion alongside dramatic increases in the overall price level. Although each country faced different political and economic circumstances, excessive money growth was the common factor associated with sustained hyperinflation.

The chapter concluded by examining several common misconceptions about inflation. Businesses have always sought profits, oil prices have always fluctuated, and supply shortages have occurred throughout history. While these factors can affect individual prices and temporarily influence measured inflation, they do not explain sustained increases in the overall price level. Persistent inflation requires persistent growth in the money supply relative to the production of goods and services.

The central lesson of this chapter is that inflation is fundamentally about the value of money. Individual prices may change for many reasons, but when the purchasing power of money declines across the economy over an extended period, the result is sustained inflation.

Key Terms

Base period

The reference period against which a price index is compared.

Consumer Price Index (CPI)

A measure of the average price of a representative market basket of goods and services purchased by households.

Cost of living

The amount of money required to purchase a given standard of living.

Deflation

A sustained decrease in the overall price level.

Disinflation

A reduction in the inflation rate; prices continue to rise but at a slower rate.

Equation of Exchange

The relationship

$$MV=PY,$$

which connects money, spending, prices, and real output.

Expected inflation

The inflation rate households, workers, businesses, borrowers, and lenders anticipate when making economic decisions and entering contracts.

GDP Deflator

A measure of the overall price level calculated as

$$\frac{Nominal\ GDP}{Real\ GDP}\times100.$$

Growth-rate form of the Equation of Exchange

The relationship

$$\%\Delta M+\%\Delta V = \%\Delta P+\%\Delta Y.$$

Hyperinflation

An extremely rapid and sustained increase in the overall price level.

Inflation

A sustained increase in the overall price level or a sustained decline in the purchasing power of money.

Inflation inertia

The tendency for an established inflation rate to persist because households, workers, and businesses incorporate expected inflation into wages, prices, and contracts.

Inflation rate

The percentage change in a price index over time.

Market basket

A representative collection of goods and services purchased by a typical household.

Menu costs

The resources businesses use to change and communicate prices when inflation causes prices to be adjusted more frequently.

Money illusion

The tendency to focus on nominal dollar values rather than their real purchasing power.

Money supply ($M$)

The quantity of money available in the economy.

Nominal interest rate

The stated interest rate on a loan or financial asset before adjusting for inflation.

Overall price level

A measure of average prices throughout the economy.

Price confusion

The difficulty consumers and producers face in determining whether a price has changed because of conditions in a particular market or because the overall price level is changing.

Producer Price Index (PPI)

A measure of prices received by producers for the goods and services they sell.

Purchasing power

The quantity of goods and services that money can buy.

Quantity Theory of Money

The theory that sustained inflation results when the money supply grows faster than real output over long periods.

Real GDP growth

The percentage increase in real output over time.

Real interest rate

The nominal interest rate adjusted for inflation. Approximately,

$$Real\ Interest\ Rate = Nominal\ Interest\ Rate - Inflation.$$

Relative price

The price of one good or service compared with another.

Substitution bias

The tendency for consumers to substitute toward relatively cheaper goods when prices change.

Unexpected inflation

The difference between the inflation rate that actually occurs and the inflation rate people anticipated when making economic decisions or entering contracts.

Velocity of money ($V$)

The average number of times each dollar is used to purchase final goods and services during a given period.

Concept Check

Answer the following questions in your own words.

Problems and Applications

Thinking Like an Economist

Economics in the Real World

Data Exploration

Policy Debate

Chapter 3 AI Economics Lab