Chapter 9: Measuring Inflation

Sections 9.4, 9.5, 9.6, 9.7

This chapter covers the measurement of inflation, focusing on the Consumer Price Index (CPI), the calculation of price indices, inflation rates, and the implications of inflation for the economy.

The Consumer Price Index (CPI)

Definition and Construction

The Consumer Price Index (CPI) is a measure of the average change over time in the prices paid by urban consumers for a market basket of consumer goods and services.

• Bureau of Labor Statistics (BLS): Surveys 14,000 households to determine spending habits.

• Market Basket: Consists of 211 types of goods and services typically purchased by an urban family of four.

• Data Collection: Each month, the BLS visits 23,000 stores in 87 cities, collecting price information for about 80,000 goods and services.

• Weighting: The importance of each item in the basket is weighted according to its share in total consumer spending.

Example of Market Basket Composition:

• Food

• Transportation

• Apparel

• Medical care

• Recreation

• Education and communication

• Other goods and services

Creating a Price Index

Step-by-Step Example: The Country of Ecotopia

To illustrate the construction of a price index, consider a simplified economy producing three goods: haircuts, tacos, and laptops.

• Base Year: The year chosen as a reference point for prices. Quantities from the base year are used to calculate expenditures in all years.

Assume Year 2 is the base year. The quantities from Year 2 are used to calculate expenditures in all years.

Price Index Formula

The price index for each year is calculated as:

Calculating Inflation from the Price Index

Inflation Rate Formula

The inflation rate is the percentage change in the price index from one year to the next:

Adjusting for Inflation

Converting Nominal Values to Real Values

To compare dollar values from different years, nominal values must be adjusted for inflation using the CPI:

To convert nominal values to real terms (base-year dollars):

Example: If the minimum wage in 1988 was $3.35 and the CPI was 119.9, and in 2024 the minimum wage is $7.25 and the CPI is 309.7, the real value of the minimum wage in 2024 dollars is:

(in 1982-84 dollars)

Potential Biases in the CPI

• Substitution Bias: Consumers may substitute cheaper goods for more expensive ones, but the CPI assumes a fixed basket.

• Increase in Quality Bias: Some price increases reflect improved quality, not just inflation.

• New Product Bias: New products are not immediately included in the basket; their prices often fall after introduction.

• Outlet Bias: The CPI may not fully account for purchases at discount stores or online retailers.

These biases can cause the CPI to overstate inflation by 0.5 to 1.0 percentage points per year. The BLS now updates the market basket every two years and uses statistical methods to reduce quality bias.

Producer Price Index (PPI) and CPI

The Producer Price Index (PPI) measures the average change in selling prices received by domestic producers. The PPI is often a leading indicator for the CPI, as changes in producer prices can eventually be passed on to consumers.

Relationship: PPI changes often precede CPI changes.

Nominal vs. Real Interest Rates

• Nominal Interest Rate (i): The stated interest rate on a loan or investment.

• Real Interest Rate (r): The nominal interest rate adjusted for inflation.

The real interest rate is calculated as:

where is the nominal interest rate and is the inflation rate.

Example: If and expected , then . If actual inflation is 5%, then .

Costs of Inflation

Anticipated Inflation

• Income Redistribution: Some wages may rise faster than inflation, others may not.

• Tax Effects: Taxes are levied on nominal, not real, gains.

• Shoe Leather Costs: Increased costs of managing cash balances due to inflation.

• Menu Costs: Costs to firms of changing prices in catalogs, menus, etc.

Unanticipated Inflation

• If actual inflation is higher than expected, borrowers gain and lenders lose.

• If actual inflation is lower than expected, lenders gain and borrowers lose.

Deflation and Its Problems

Deflation is a general decrease in the average price level. It can be problematic because:

• It increases real interest rates, discouraging borrowing and spending.

• Consumers may delay purchases, reducing current consumption and GDP.

Example: If the nominal interest rate is 5% and the price level decreases by 2%, the real interest rate is 7%.

Historical examples include the United States in the 1930s and Japan in the 1990s.

Summary Table: Key CPI and Inflation Concepts

Additional info: The notes also reference the use of CPI as a policy tool, the importance of accurate inflation measurement for contracts and social security adjustments, and the impact of inflation expectations on economic behavior.