MGU Social Science Series — Economics: Principles of Microeconomics and Macroeconomics
Part V: Macroeconomic Foundations
Inflation · Price Indexes · Purchasing Power · Real vs. Nominal
Chapter 22 of 30
MGU Social Science Series  ·  Economics: Principles of Microeconomics and Macroeconomics  ·  Library Textbook Edition

Chapter 22:
Inflation, Price Indexes,
and Cost of Living

How economists measure the general price level, why a rising price level is different from a single price rising, and what inflation costs households, workers, savers, and borrowers

■ Part V: Macroeconomic Foundations ■

■ 10 Sections  •  Chapter 22 of 30 ■

Builds on Chapter 21: Unemployment  ·  Prepares for Chapter 23: Aggregate Demand and Aggregate Supply

Chapter 22 — Front Matter

Purpose and Overview

In the summer of 1923, a loaf of bread in Germany cost more than 200 billion marks. Workers were paid twice a day because prices rose so fast that wages lost their value by lunchtime. People used wheelbarrows to carry enough currency to buy groceries. Savings accumulated over a lifetime were wiped out within weeks.

That episode — one of the most extreme inflations in modern history — illustrates why economists, governments, households, and businesses pay such close attention to changes in the general price level. Inflation does not just mean that prices go up. It means that the purchasing power of money goes down. It reshapes who benefits and who loses. It disrupts planning, savings, contracts, and trust.

Most economies do not experience hyperinflation. But even moderate inflation matters. A worker who receives a 3 percent pay raise in a year when prices rise 5 percent has actually taken a pay cut in real terms. A family living on fixed retirement income loses purchasing power every year that prices rise faster than their income adjusts. A firm that signed a long-term supply contract at fixed prices may find its costs have risen far beyond what the contract assumed.

Understanding inflation — what it is, how it is measured, what it costs, and how it differs from a single price rising — is essential economic literacy. This chapter builds that understanding step by step.

Opening Question

If your favorite snack doubled in price next month, would that mean the economy has inflation? What would you need to know about every other price in the economy to answer that question with confidence? By the end of this chapter, you will be able to calculate an inflation rate, convert a nominal wage into a real wage, and explain why a 5 percent raise can sometimes be a pay cut.

10Sections
18Key Terms
40Practice Items
30Chapters Total

Learning Objectives

  1. 1Define inflation as a sustained rise in the general price level and distinguish it from a single relative price change.
  2. 2Explain how a price index summarizes price changes across a market basket using a base period.
  3. 3Calculate the CPI from market basket costs and calculate the inflation rate from CPI values.
  4. 4Explain purchasing power and describe how it changes as the price level rises.
  5. 5Distinguish nominal values from real values and convert between them.
  6. 6Explain cost of living adjustments and the wage-price spiral.
  7. 7Distinguish inflation, deflation, disinflation, and hyperinflation.
  8. 8Identify the economic costs of inflation, including menu costs and shoe leather costs.
  9. 9Explain how inflation redistributes resources between debtors and creditors.
  10. 10Evaluate the strengths and limitations of the CPI as a measurement tool.
Chapter 22 — Contents

Sections at a Glance

Sections 22.1 – 22.4
What Inflation Is and How It Is Measured
General Price Level · Relative Prices · Price Indexes · Market Baskets
Section 22.1

What Inflation Means

Inflation is a sustained increase in the general price level of goods and services across an economy over time.

Several words in that definition matter. Sustained means inflation is not a single price spike. If gasoline prices surge for one month and then fall back, that is a price fluctuation, not inflation. General price level means across many goods and services — not just one item. If avocado prices double because of a drought, but the increase is offset by falling prices elsewhere, the general price level may have barely moved. Over time means inflation is measured as a rate of change — typically compared to the same period a year earlier.

When economists say the inflation rate is 4 percent, they mean the general price level is about 4 percent higher than it was twelve months earlier.

What Inflation Is Not

Inflation is not the same as a high price level — a country can have high prices today but low inflation if those prices are now stable. Inflation is not the same as one price rising — that is a relative price change. Inflation is not the same as prices being unaffordable — a good can be expensive without any inflation occurring. And inflation is not always bad: economists generally consider low, stable inflation of about 1 to 3 percent annually to be normal and manageable.

Practice 22.1Concept Check
  1. In your own words, explain why "sustained" and "general" are both necessary parts of the definition of inflation.
  2. A country's prices have been stable at a high level for ten years. Does this country have high inflation? Explain.
  3. Give an example of a price increase that would NOT count as inflation by itself.
Section 22.2

Price Levels and Individual Prices

Every day, prices change in particular markets. The price of wheat rises after a drought; the price of televisions falls as technology improves. These are movements in relative prices — the prices of particular goods compared to other goods. Relative price changes signal where resources are scarce or abundant and guide consumers and producers, but they are not the same thing as inflation.

The general price level is a weighted average summarizing what is happening to prices across the whole economy. Inflation occurs when that average rises.

A Useful Mental Model: Weighted Average

Imagine households buy only food, housing, and clothing. Food prices rise 10%, housing rises 5%, clothing falls 3%. If households spend 50% on housing, 30% on food, and 20% on clothing:

(0.50 × 5%) + (0.30 × 10%) + (0.20 × −3%) = 2.5% + 3.0% − 0.6% = 4.9%

The general price level rose about 4.9 percent, even though clothing prices fell. Items with larger budget shares receive larger weights in the overall average.

Practice 22.2Weighted Price Changes
  1. A household spends 40% on housing, 35% on food, and 25% on transportation. Housing rises 4%, food rises 6%, transportation falls 2%. Calculate the weighted price change.
  2. Explain why a sharp rise in one good's price might not raise the general price level much.
Section 22.3

Price Indexes

A price index is a measure of the general price level relative to a base period. It has two key features: a base period, typically assigned an index value of 100, and a set of goods and services whose prices are tracked over time.

If a price index equals 100 in the base period and rises to 112 three years later, prices have risen 12 percent above the base period level. If the same index falls from 112 to 108, that is deflation — the price level is now 8 percent above the original base, not 12 percent.

The Most Widely Known Index

Several types of price indexes exist in economics. The most widely known for measuring consumer prices is the Consumer Price Index (CPI), covered in Section 22.5.

Practice 22.3Reading Index Values
  1. An index equals 100 in the base year and 118 five years later. How much have prices risen?
  2. An index falls from 130 to 124. Is this inflation or deflation? Express the change relative to the base year.
Section 22.4

Market Baskets

The practical foundation of a price index is the market basket — a defined collection of goods and services meant to represent typical purchases. To construct a price index, economists survey households to learn what they buy, define a fixed basket of items and quantities, track the prices of those items, calculate the basket's cost each period, and divide by the base period cost (multiplied by 100) to express it as an index.

The fixed basket approach keeps measurement consistent over time, but it can fail to capture how consumers substitute toward cheaper alternatives when prices rise — a limitation explored further in Section 22.10.

CPI CategoryExamples
Food and beveragesGroceries, restaurant meals, nonalcoholic beverages
HousingRent, utilities, household supplies, furniture
ApparelClothing and footwear
TransportationVehicle purchases, gasoline, public transit, insurance
Medical carePrescription drugs, physician services, hospital care
RecreationSports equipment, televisions, admission fees, pets
Education and communicationTuition, postage, telephone services, computers
Other goods and servicesHaircuts, personal care products, tobacco
A Limitation Worth Noting Early

If coffee becomes expensive, many households switch to tea — but a fixed basket keeps measuring the original coffee quantities. This can cause the index to overstate how much rising coffee prices actually raise the cost of living, since the index does not reflect substitution.

Practice 22.4Market Basket Construction
  1. Why must the market basket stay fixed in quantity to give meaningful comparisons over time?
  2. Housing is typically the largest weight in the U.S. CPI. Why might that be the case for a typical household budget?
Sections 22.5 – 22.7
Calculating the CPI, the Inflation Rate, and Purchasing Power
CPI Formula · Inflation Rate Formula · Purchasing Power Erosion
Section 22.5

Consumer Price Index at an Introductory Level

The Consumer Price Index (CPI) is the most widely used measure of inflation for households. It tracks how much a fixed market basket of consumer goods and services costs over time. In the United States, the CPI is produced by the Bureau of Labor Statistics (BLS), which collects price data from thousands of stores, rental units, hospitals, and service providers each month.

CPI Formula

CPI = (Cost of basket in current period ÷ Cost of basket in base period) × 100

Example 22.5.1
Calculating the CPI
  • SituationA market basket in the base year costs $800. In a later year, the same basket costs $880.
  • CalculationCPI = (880 ÷ 800) × 100 = 110
  • MeaningAn index value of 110 means the price level is 10 percent higher than in the base year.
Key takeaway: An index above 100 always means prices are higher than in the base year — by exactly that percentage above 100.
YearCost of Market BasketCPI
Base Year$800100.0
Year 2$824103.0
Year 3$848106.0
Year 4$880110.0
Year 5$912114.0
Practice 22.5CPI Calculation
  1. Basket costs $500 in base year, $545 later. Find the CPI.
  2. Basket costs $1,200 in base year, $1,080 later. Find the CPI.
  3. An index of 96 means what about prices relative to the base year?
  4. If the CPI is 103, by what percentage have prices risen?
Section 22.6

Calculating Inflation Rates

The inflation rate measures how much the price level changed from one period to the next, expressed as a percentage. It is a standard percentage-change formula applied to index numbers.

Inflation Rate Formula

Inflation Rate = [(CPI now − CPI before) ÷ CPI before] × 100

Example 22.6.1
From Year 2 to Year 3, and Year 4 to Year 5
  • Year 2–3(106.0 − 103.0) ÷ 103.0 × 100 ≈ 2.9%
  • Year 4–5(114.0 − 110.0) ÷ 110.0 × 100 ≈ 3.6%
  • InsightBoth periods rose 4.0 index points, but the inflation rate was higher in Year 4–5 because the starting base was larger. Equal point gains do not mean equal percentage gains.
Key takeaway: Always divide by the prior period's index value, not by 100, when calculating an inflation rate between two non-base years.
Don't Confuse the Rate with the Level

A CPI of 200 with 1% inflation means prices are double the base year but rising slowly. A CPI of 110 with 8% inflation means prices are only 10% above base but rising quickly. Policy concern usually centers on the inflation rate, not the absolute price level.

Practice 22.6Inflation Rate Calculation
  1. CPI rises from 100.0 to 102.5. Find the inflation rate.
  2. CPI rises from 105.0 to 109.2. Find the inflation rate.
  3. CPI rises from 109.2 to 111.4. Find the inflation rate.
  4. Compare your answers to items 2 and 3. Which period had higher inflation?
Section 22.7

Purchasing Power

Purchasing power refers to the quantity of goods and services that a unit of money can buy. When prices rise, the purchasing power of money falls. Purchasing power and the price level move in opposite directions: when the price level rises 10 percent, the purchasing power of a dollar falls by approximately 9 percent.

Example 22.7.1
Purchasing power after a price rise
  • SituationA basket costs $500 in the base year and $550 a year later — a 10% price rise.
  • Effect on savingsA household holding $500 can now afford only about 91% of the same basket.
  • Effect on needed incomeTo maintain the same standard of living, the household needs about 10% more money than before.
Key takeaway: A given price-level increase reduces purchasing power by a slightly smaller percentage than the price increase itself.
Annual Inflation RateApprox. Years to Halve Purchasing Power
1%~70 years
2%~35 years
4%~18 years
7%~10 years
10%~7 years
20%~3.5 years
The Rule of 70

Dividing 70 by the annual rate approximates the number of years needed for a quantity to double — or, applied to the rate of decline, for purchasing power to halve. Even 3 percent annual inflation halves purchasing power in roughly 23 years.

Practice 22.7Purchasing Power
  1. Using the Rule of 70, approximate how many years it would take for purchasing power to halve at 5 percent annual inflation.
  2. A household has $2,000 in savings. Prices rise 8 percent. Approximately what percentage of their original purchasing power remains?
Sections 22.8 – 22.10
Real Values, Deflation, and the Costs of Inflation
Nominal vs. Real · Deflation and Disinflation · Costs and Measurement Limits
Section 22.8

Nominal and Real Wages

Nominal wages are wages measured in current dollars. Real wages adjust nominal wages for inflation to reflect actual purchasing power. A worker who received $15 per hour last year and $16 this year saw a nominal increase of about 6.7 percent — but if inflation was 4 percent, the real increase was only about 2.7 percent. If inflation had been 8 percent, that same nominal raise would represent a real wage decrease.

Nominal-to-Real Conversion Formula

Real Value = (Nominal Value ÷ Price Index) × 100

Example 22.8.1
Converting a nominal wage to a real wage
  • SituationA worker earns a nominal wage of $20 per hour in a year when the CPI is 125.
  • CalculationReal Wage = (20 ÷ 125) × 100 = $16 (base-year dollars)
  • Meaning$20 today buys only as much as $16 would have bought in the base year.
Key takeaway: This conversion applies to any nominal amount — income, prices, GDP, rents, interest payments, and savings.
YearNominal WageCPIReal Wage (base-year dollars)
Year 1 (base)$12.00100.0$12.00
Year 2$12.60103.0$12.23
Year 3$13.20108.0$12.22
Year 4$14.00116.0$12.07
Year 5$15.00125.0$12.00
A Nominal Illusion

In the table above, the nominal wage rose 25 percent from Year 1 to Year 5 — but the CPI also rose 25 percent, so the real wage in Year 5 equals the real wage in Year 1. The worker earned more dollars but could buy exactly the same amount of goods and services.

Cost of Living Adjustments (COLAs)

Many wages, benefits, and contracts include automatic increases tied to a price index — often the CPI — to preserve purchasing power. Social Security benefits include an annual COLA. But COLAs can also embed inflation into cost structures: if wages rise automatically with prices, businesses may raise prices further, triggering further wage increases — a self-reinforcing pattern called a wage-price spiral.

Practice 22.8Nominal and Real Wages
  1. Nominal wage $18.00, CPI 112. Find the real wage.
  2. Nominal wage $24.50, CPI 140. Find the real wage.
  3. A 5% nominal raise occurs during 7% inflation. Did real wages rise or fall? By about how much?
  4. Explain in one sentence why a COLA might contribute to a wage-price spiral.
Section 22.9

Deflation and Disinflation

Deflation occurs when the general price level falls — negative inflation. Although falling prices might sound appealing, sustained deflation carries serious risks: consumers may delay purchases waiting for lower prices (reducing demand and employment), the real burden of fixed-dollar debts rises, and firms with fixed wage or debt obligations see profits squeezed as revenues fall. Japan's prolonged near-zero inflation and periodic deflation beginning in the 1990s — the "Lost Decade" — illustrates why central banks treat deflation as a serious threat.

Disinflation is a slowing of the inflation rate — prices still rise, just more slowly. If inflation falls from 8 percent to 4 percent, that is disinflation, not deflation. Disinflation is often a desired policy outcome when inflation has been too high.

TermWhat It MeansExample
InflationPrice level risingCPI goes from 100 to 105
DeflationPrice level fallingCPI goes from 105 to 102
DisinflationInflation rate slowingInflation falls from 8% to 3%
HyperinflationExtremely rapid inflationPrices double in months or weeks
Practice 22.9Deflation vs. Disinflation
  1. Inflation was 6% last year and 4% this year. Is this disinflation or deflation? Explain.
  2. Explain why falling prices can hurt a household with a large fixed-rate mortgage.
  3. Why might a central bank prefer disinflation to deflation when fighting high inflation?
Section 22.10

Costs and Measurement Limits of Inflation

Inflation imposes real costs. Erosion of purchasing power harms anyone holding money or receiving fixed payments. Redistribution between debtors and creditors occurs because borrowers repay fixed-rate loans with dollars that are worth less when inflation rises unexpectedly — benefiting debtors and harming creditors. Menu costs are the administrative costs of updating prices; shoe leather costs are the time and effort spent managing cash to avoid its erosion. Inflation can also distort price signals, increase planning uncertainty, and harm international competitiveness if a country's inflation outpaces its trading partners'.

GroupEffect of Unexpected Inflation
Fixed nominal income recipients (no COLA)Real income declines
Savers in low-interest cash accountsLose purchasing power if interest is below inflation
Creditors / bondholders at fixed ratesRepaid in dollars worth less in real terms
Borrowers at fixed ratesOften benefit as real debt value falls
Workers with strong bargaining powerMay keep pace with or outrun inflation
Owners of real assets (housing, land)Often preserve or increase real wealth
Limitations of the CPI

Substitution bias causes a fixed basket to overstate inflation when consumers switch to cheaper alternatives. The new goods problem means new products may not enter the basket immediately. Quality changes are difficult to separate from pure price changes. The CPI is also a national average, so it may not reflect geographic variation or the spending patterns of households whose budgets differ from the typical urban household represented in the basket.

Still a Useful Tool

None of these limitations make the CPI useless. It remains a carefully constructed, consistent tool for comparing price levels over time. Alternative indexes — such as the Personal Consumption Expenditures (PCE) index used by the Federal Reserve, or the Producer Price Index (PPI) — provide additional perspectives.

Practice 22.10Costs and Limitations
  1. Give an example of a menu cost and an example of a shoe leather cost.
  2. Explain why unexpected inflation benefits debtors and harms creditors, using a specific loan example.
  3. Describe a real-world example of substitution bias in the CPI.
Chapter 22 — Back Matter

Chapter Summary

Key Terms Review

inflation
A sustained increase in the general price level of goods and services across an economy over time.
general price level
An average of prices across many goods and services in an economy, weighted by their importance in typical household spending.
relative price
The price of one good or service compared to other goods and services.
price index
A measure of the general price level relative to a base period, calculated from the prices of a defined market basket.
base period
The reference time period assigned an index value of 100, against which later price levels are compared.
market basket
A defined collection of goods and services, in fixed quantities, used to track price changes over time.
Consumer Price Index (CPI)
A price index measuring how much a fixed market basket of consumer goods and services costs over time.
inflation rate
The percentage change in a price index from one period to the next.
purchasing power
The quantity of goods and services that a unit of money can buy; falls when the price level rises.
nominal wage
A wage measured in current dollars, without adjustment for inflation.
real wage
A wage adjusted for inflation to reflect actual purchasing power, expressed in base-period dollars.
cost of living adjustment (COLA)
An automatic increase in a payment tied to a price index, designed to preserve purchasing power.
deflation
A sustained decrease in the general price level; negative inflation.
disinflation
A slowing of the rate of inflation; prices still rise, but more slowly than before.
hyperinflation
Extremely rapid inflation in which prices rise dramatically over a short period.
menu costs
The costs businesses incur when updating prices during periods of inflation.
shoe leather costs
The time and effort people spend managing cash holdings to avoid the erosion of purchasing power during inflation.
substitution bias
The tendency of a fixed-basket price index to overstate inflation because it does not account for consumers switching to cheaper substitutes.

Inflation Calculation Practice

Use the CPI formula and the inflation rate formula. Show your work for each problem.

  1. Basket cost: $600 base year, $618 Year 2. Find CPI.
  2. Basket cost: $600 base year, $645 Year 3. Find CPI.
  3. CPI rises from 103.0 to 107.5. Find inflation rate.
  4. CPI rises from 112.0 to 119.0. Find inflation rate.
  5. Nominal wage $14.00, base year (CPI 100). Find real wage.
  6. Nominal wage $16.00, CPI 112.0. Find real wage in base-year dollars.

Case Study

Case Study 22.1
A Household Tracking Its Own Cost of Living
  • BackgroundThe Alvarez family spends 55% of its budget on housing, 25% on food, and 20% on transportation. Over one year, housing costs rise 7%, food prices rise 4%, and transportation costs fall 1%.
  • Weighted change(0.55 × 7%) + (0.25 × 4%) + (0.20 × −1%) = 3.85% + 1.0% − 0.2% = 4.65%
  • Comparison to national CPIIf the national CPI reports 3.0% inflation that year, the Alvarez family is experiencing a higher personal inflation rate than the national average — largely because housing, their largest expense, rose faster than the overall basket.
  • ImplicationNational inflation statistics are averages. Individual households can experience meaningfully different inflation depending on their specific spending patterns.
Discussion: Why might two households with identical income still experience different real-world inflation?

Policy Decision Point

Policy Scenario — Section 22.8

A government is considering whether to remove the automatic COLA from a major pension program to reduce federal spending. Retirees argue that removing the COLA would erode their purchasing power every year inflation occurs. Budget officials argue that COLAs make long-term spending unpredictable and costly. What are the tradeoffs? Who benefits and who is harmed by each choice? Is this a positive or a normative question — or both?

Review Questions

  1. Define inflation in your own words. Why must the price increase be both "general" and "sustained"?
  2. What is the difference between a relative price change and inflation?
  3. Explain how a price index is built from a market basket and a base period.
  4. Write the CPI formula and the inflation rate formula from memory.
  5. What is purchasing power, and how is it affected by inflation?
  6. What is the difference between a nominal value and a real value?
  7. Distinguish inflation, deflation, disinflation, and hyperinflation.
  8. List three economic costs of inflation.
  9. Why does unexpected inflation help debtors and hurt creditors?
  10. Name two limitations of the CPI as a measurement tool.

Discussion Questions

  1. Some economists argue a small positive inflation rate (1–3%) is healthier for an economy than 0% inflation. Why might that be true, given what you've learned about deflation?
  2. Should government benefits always include automatic COLAs? What are the tradeoffs for taxpayers versus benefit recipients?
  3. If your personal cost of living rises faster than the national CPI, does that mean the CPI is "wrong"? Explain using the concepts in this chapter.
  4. Is hyperinflation primarily an economic problem, a political problem, or both? Explain your reasoning.

Chapter 22 Checkpoint

Chapter 22 Checkpoint
Inflation and Price Indexes — Complete without assistance; assesses all key skills and concepts from Chapter 22
Section 1 — Vocabulary and Concepts
  1. Define inflation. Why is a single price rising not the same thing as inflation?
  2. What is a market basket, and why must it stay fixed for the CPI to be a consistent measure?
  3. Explain the difference between nominal and real values, and why the distinction matters to workers.
  4. Distinguish deflation from disinflation using an example of each.
Section 2 — Calculation
  1. A market basket costs $700 in the base year and $749 the following year. Calculate the CPI.
  2. The CPI rises from 108.0 to 113.4 over one year. Calculate the inflation rate.
  3. A worker earns a nominal wage of $21.00 per hour in a year when the CPI is 105. Calculate the real wage in base-year dollars.
Section 3 — Analysis
  1. A student says, "If the CPI goes up, that means I'm definitely worse off." Evaluate this claim using the concepts of nominal income, real income, and individual spending patterns.
  2. Explain why a fixed-rate borrower might benefit from unexpected inflation while the lender does not.
Section 4 — Applied Practice
  1. Choose a household budget category (housing, food, transportation, etc.) and explain how a sharp price increase in that category specifically would affect a typical household's measured versus personal inflation rate.
  2. Describe one real or hypothetical policy that uses a COLA. Explain who it protects and what tradeoff exists in funding it.
Section 5 — Policy Reasoning
  1. A central bank must choose between tolerating 6% inflation or raising interest rates sharply, risking a recession, to bring inflation down quickly. Using concepts from this chapter, explain what each affected group — savers, debtors, creditors, workers — would likely prefer and why.
Looking Ahead
Chapter 23: Aggregate Demand and Aggregate Supply

Chapter 22 examined how economists measure inflation and why changes in the general price level matter for purchasing power, wages, income, and economic planning. Chapter 23 introduces the aggregate demand and aggregate supply model — a framework for analyzing the whole economy, including how output and the price level are jointly determined. You will see how the inflation concepts from this chapter connect to broader macroeconomic analysis, and you will begin to understand how demand shocks and supply shocks affect both output and prices at the economy-wide level. The tools of this chapter — real versus nominal, price levels, inflation rates — will appear throughout the rest of the macroeconomics section.

MGU Library Connection
  • Inflation Guide — Companion Resources, MGU Library
  • Economics Data Interpretation Checklist — Companion Resources
  • Chapter 20: Measuring the Economy: GDP and National Income — nominal vs. real GDP foundations
  • Chapter 23: Aggregate Demand and Aggregate Supply — continues directly from this chapter
  • Chapter 26: Central Banking and Monetary Policy — develops inflation targeting in full
  • Appendix E: Formula and Calculation Reference — inflation rate and real-versus-nominal formulas
  • Appendix H: Macroeconomic Measurement Reference — CPI and Consumer Price Index entries