What Is Consumer Price Index?

Definition

Consumer Price Index (CPI) refers to a measure of the total change in prices of a basket of goods and services consumed by households, developed by Étienne Laspeyres in 1871.

How It Works

The CPI calculation involves tracking the prices of a representative basket of goods and services, which includes food, housing, clothing, transportation, and healthcare. The prices are collected from a sample of retailers, service providers, and other sources, with the frequency of collection varying by country, such as monthly in the United States (Bureau of Labor Statistics) and quarterly in Australia (Australian Bureau of Statistics). The CPI is then calculated by taking a weighted average of the price changes of the individual items in the basket, using weights that reflect the relative importance of each item in the average household budget, such as the 42% weight assigned to housing in the US CPI (Bureau of Labor Statistics).

The CPI serves as a proxy for inflation, which is the rate of change of the CPI over time. Central banks, such as the Federal Reserve in the United States, use the CPI to set monetary policy, aiming to keep inflation within a target range, typically around 2% annual rate (Federal Reserve). For example, the European Central Bank uses the Harmonized Index of Consumer Prices (HICP) to measure inflation in the Eurozone, which has a target rate of below 2% (European Central Bank). The CPI also affects the cost of living adjustments made to social security benefits, pensions, and other government payments, with the US Social Security Administration using the CPI to adjust benefits annually (Social Security Administration).

The CPI has several limitations, including the potential for bias in the sample of prices collected and the difficulty of capturing changes in quality of goods and services over time. To address these limitations, some countries use alternative measures, such as the Gross Domestic Product (GDP) deflator, which measures the change in prices of all goods and services produced within a country (World Bank). The Personal Consumption Expenditures (PCE) index, used by the US Federal Reserve, is another alternative, which includes a broader range of expenditures, such as healthcare and financial services (Bureau of Economic Analysis).

Key Components

• Weighted average: the CPI is calculated by taking a weighted average of the price changes of the individual items in the basket, with weights that reflect the relative importance of each item in the average household budget.
• Basket of goods and services: the CPI tracks the prices of a representative basket of goods and services, which includes food, housing, clothing, transportation, and healthcare.
• Price collection: the prices are collected from a sample of retailers, service providers, and other sources, with the frequency of collection varying by country.
• Inflation target: central banks use the CPI to set monetary policy, aiming to keep inflation within a target range, typically around 2% annual rate.
• Cost of living adjustments: the CPI affects the cost of living adjustments made to social security benefits, pensions, and other government payments.
• Quality adjustment: the CPI has difficulty capturing changes in quality of goods and services over time, which can lead to bias in the measurement of inflation.

Common Misconceptions

Myth: The CPI measures the actual change in the cost of living for individual households.

Fact: The CPI measures the average change in prices of a basket of goods and services, which may not reflect the actual change in cost of living for individual households, as households have different consumption patterns (Bureau of Labor Statistics).

Myth: The CPI is a perfect measure of inflation.

Fact: The CPI has limitations, including the potential for bias in the sample of prices collected and the difficulty of capturing changes in quality of goods and services over time, which can lead to inaccurate measurements of inflation (Bureau of Labor Statistics).

Myth: The CPI only measures the prices of goods.

Fact: The CPI also measures the prices of services, such as healthcare and financial services, which are included in the basket of goods and services (Bureau of Labor Statistics).

Myth: The CPI is only used by central banks.

Fact: The CPI is used by a wide range of organizations, including government agencies, businesses, and individuals, to make informed decisions about prices, wages, and benefits (Bureau of Labor Statistics).

In Practice

In the United States, the CPI is used to adjust the Social Security benefits, with a 1.3% cost of living adjustment made in 2021, resulting in an increase of $20 per month for the average beneficiary (Social Security Administration). The CPI is also used by the Federal Reserve to set monetary policy, with the target inflation rate set at 2% annual rate (Federal Reserve). In Australia, the CPI is used to adjust the pensions and benefits paid to eligible recipients, with a 1.6% increase made in 2020, resulting in an increase of AUD 14 per week for the average pensioner (Australian Government Department of Social Services).