Understanding Purchasing Power and the Consumer Price Index

Adam Hayes

Adam Hayes, Ph.D., CFA, is a financial writer with 15+ years Wall Street experience as a derivatives trader. Besides his extensive derivative trading expertise, Adam is an expert in economics and behavioral finance. Adam received his master's in economics from The New School for Social Research and his Ph.D. from the University of Wisconsin-Madison in sociology. He is a CFA charterholder as well as holding FINRA Series 7, 55 & 63 licenses. He currently researches and teaches economic sociology and the social studies of finance at the University of Lucerne in Switzerland.Adam's new book, "Irrational Together: The Social Forces That Invisibly Shape Our Economic Behavior" (University of Chicago Press) is a must-read at the intersection of behavioral economics and sociology that reshapes how we think about the social underpinnings of our financial choices.

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Updated July 02, 2025

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Michael J Boyle

Reviewed byMichael J Boyle

Michael Boyle is an experienced financial professional with more than 10 years working with financial planning, derivatives, equities, fixed income, project management, and analytics.

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Part of the Series

Inflation

Inflation: What It Is and How to Control Inflation Rates

Understanding Inflation

Types of Inflation

What Does Inflation Impact?

Understanding Hyperinflation

Understanding CPI

Related Terms (A-I)

Related Terms (J-Z)

Definition

Purchasing power refers to how much money you can buy with a unit of currency; essentially, a measure of what your money is worth in terms of goods and services.

What Is Purchasing Power?

Purchasing power describes the amount of products or services that a single unit of money can acquire, reflecting the real-world value of currency in the marketplace. It can weaken over time due toinflation. That's because rising prices effectively decrease the number of goods or services that one unit of money can buy. Purchasing power is also known as a currency's buying power.

In investment terms, purchasing orbuying power is the dollar amount of credit available to a customer based on the existingmarginable securities in the customer's brokerage account.

Key Takeaways

Inflation erodes the purchasing power of a currency over time.
Central banks adjust interest rates to try to keep prices stable and maintain purchasing power.
One U.S. measure of purchasing power is the Consumer Price Index (CPI).
Globalization has linked currencies more closely than ever, so protecting purchasing power worldwide is crucial.

Understanding Purchasing Power

Purchasing power affects every aspect of economics, from consumers buying goods to investors buying stock to a country’s economic prosperity.

Inflation reduces a currency's purchasing power. Similarly, loss of purchasing power has the same effect as an increase in prices. To measure purchasing power in the traditional economic sense, you could compare the price of a good or service against a price index such as theConsumer Price Index (CPI).

One way to understand purchasing power is to imagine that you worked the same job that your grandfather worked 40 years ago. Today, you would need a much higher salary to maintain the same quality of living. By the same token, a homebuyer looking for homes 10 years ago in the $300,000 to $350,000 price range had more and better options to consider than people have now in the same price range.

When a currency’s purchasing power decreases due to excessive inflation, serious negative economic consequences can arise. These can include a highercost of living, higher interest rates that affect the global market, andfalling credit ratings. All of these factors can contribute to an economic crisis.

Purchasing Power and CPI

Governments institute policies and regulations toprotect a currency’s purchasing power and keep an economy healthy. They also monitor economic data to stay on top of changing conditions. For example, theU.S. Bureau of Labor Statistics (BLS) measures price changes and announces those changes with CPI.

CPI is one of the measures of inflation and purchasing power. It calculates the change in the weighted average of prices of consumer goods and services, and in particular, transportation, food, and medical care, at a given time. CPI can point to changes in the cost of living as well asdeflation.

The CPI is just one official measure of purchasing power in the U.S.

Purchasing Price Parity

A concept related to purchasing power ispurchasing power parity (PPP). PPP is an economic theory that estimates the amount by which an itemshould be adjusted for parity, given two countries’ exchange rates. PPP can be used to compare countries’ economic activity, income levels, and other relevant data concerning the cost of living, or possible rates of inflation and deflation.

The World Bank's International Comparison Program releases data on purchasing power parities between different countries.

Purchasing Power Loss or Gain

Purchasing power loss or gain refers to the decrease or increase in how much consumers can buy with a given amount of money. Consumers lose purchasing power when prices increase. They gain purchasing power when prices decrease.

Causes of purchasing power loss can include government regulations, inflation, and natural and human-made disasters. Causes of purchasing power gain include deflation and technological innovation.

One example of purchasing power gain would be if laptop computers that cost $1,000 two years ago cost $500 today. In the absence of inflation, $1,000 will now buy a laptop plus an additional $500 worth of goods.

Fast Fact

The Great Inflation of the 1970s to early 1980s devastated the purchasing power and standard of living of Americans. The rate of inflation skyrocketed to 14%.

Examples of Purchasing Power Loss

Germany After WWI

Historical examples of severe inflation andhyperinflation—which can destroy a currency’s purchasing power—show us the various causes and effects of such phenomena. Sometimes, expensive and devastating wars will cause an economic collapse, particularly for the losing country. This happened to Germany after World War I (WWI).

In the aftermath of WWI during the 1920s, Germany experienced extreme economic hardship and almost unprecedented hyperinflation, due in part to the enormous amount of reparations Germany had to pay.

Unable to pay these reparations with the suspect German mark, Germany printed paper notes to buy foreign currencies, resulting in high inflation rates that rendered the German mark valueless, with a nonexistent purchasing power.

The 2008 Financial Crisis

The effects of the loss of purchasing power in the aftermath of the2008 global financial crisis and the European sovereign debt crisis are remembered to this day. Due to increasedglobalization and the introduction of the euro, currencies are inextricably linked, and economic trouble can cross geographic boundaries. As a result, governments worldwide institute policies to control inflation, protect purchasing power, and prevent recessions.

For example, in 2008, theU.S. Federal Reserve kept interest rates near zero and instituted a plan calledquantitative easing (QE). Quantitative easing, initially controversial, saw the U.S.Federal Reserve System (Fed) buy government and other market securities to increase the money supply and lower interest rates.

The increase in capital spurred increased lending and created moreliquidity. The U.S. stopped its policy of quantitative easing once the economy stabilized.

TheEuropean Central Bank (ECB) also pursued quantitative easing to help stop deflation in the eurozone after the European sovereign debt crisis and bolster the euro's purchasing power. TheEuropean Economic and Monetary Union established strict regulations in the eurozone related to accurately reporting sovereign debt, inflation, and other financial data.

As a general rule, countries attempt to keep inflation fixed at a rate of 2%. Moderate levels of inflation are acceptable. High levels of deflation can lead to economic stagnation.

Special Considerations

Investments That Protect Against Purchasing Power Risk

Retirees can be particularly aware of purchasing power loss since many of them live off of a fixed amount of money. They must make sure that their investments earn arate of return equal to or greater than the rate of inflation so that the value of theirnest egg does not decrease each year.

Debt securities and investments with fixed rates of return are the most susceptible to purchasing power risk or inflation. Fixed annuities,certificates of deposit (CDs), and Treasury bonds all fall into this category. For instance, a long-term bond with a low fixed rate of return might fail to increase your investment during periods of inflation.

Some investments or investing strategies can helpprotect investors against purchasing power risk. For example,Treasury inflation-protected securities (TIPS) adjust to keep up with rising prices. Commodities such as oil and metals may maintain pricing power during periods of inflation.

What's Purchasing Power?

Purchasing power refers to how much you can buy with your money. As prices rise, your money can buy less. As prices drop, your money can buy more.

How Does Inflation Erode Purchasing Power?

Inflation is the gradual rise in the prices of a broad range of products and services. If inflation persists at a high level or gets out of control, it can eat away at purchasing power, what you can buy with the money you have. The same product that cost $2 six months ago might now cost $4 due to inflation. This rise in prices, in turn, can erode people's savings and consequently, their standard of living.

What Is the Consumer Price Index (CPI)?

CPI measures the prices of certain consumer goods and services over time to discern changes in prices that indicate inflation. The prices for those goods and services are obtained from American consumers by way of the Consumer Expenditure Survey conducted by the Census Bureau for the Bureau of Labor Statistics, which publishes CPI data.

The Bottom Line

Long-time investors know that loss of purchasing power can greatly impact their investments. Rising inflation affects purchasing power by decreasing the number of goods or services you can purchase with your money.

Investors must look for ways to make a return higher than the current rate of inflation. More advanced investors may track international economies for the potential effect on their long-term investments.

Article Sources

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