Common Misconceptions About Consumer Price Index

The most common misconception about the consumer price index (CPI) is that it accurately reflects the inflation rate experienced by all households, which is not supported by the evidence, as the CPI is based on a basket of goods and services that may not represent the typical consumption pattern of all households, such as low-income households, which spend a larger proportion of their income on necessities like food and housing, as noted by the Bureau of Labor Statistics.

Misconceptions

• Myth: The CPI is a perfect measure of inflation, capturing all price changes in the economy.
• Fact: The CPI only tracks a specific basket of goods and services, and its accuracy can be affected by substitution bias, where consumers switch to cheaper alternatives when prices rise, a phenomenon observed by economists like Hicks, who noted that the CPI can overstate inflation by up to 1% due to this bias.
• Source of confusion: This myth persists due to the widespread media narrative that the CPI is the definitive measure of inflation, often citing it as the sole indicator of price changes.
• Myth: The CPI is calculated using a representative sample of the entire population.
• Fact: The CPI is based on the expenditures of urban households, which account for about 87% of the US population, but may not accurately represent the experiences of rural households, who face different price pressures, as noted by the US Department of Agriculture, which reports that rural households spend more on transportation and less on housing than urban households.
• Source of confusion: The CPI's urban focus is often overlooked in textbook explanations, which tend to emphasize the index's comprehensive nature.
• Myth: The CPI is adjusted for quality changes in products, ensuring that it only captures pure price changes.
• Fact: While the CPI does account for some quality changes, such as improvements in electronics, it may not fully capture the effects of rapid technological progress, which can lead to significant quality adjustments, as seen in the case of Moore's Law, which describes the exponential improvement in computing power.
• Source of confusion: The complexity of quality adjustments is often glossed over in media reports, which may imply that the CPI perfectly accounts for all quality changes.
• Myth: The CPI is a timely indicator of inflation, reflecting current price pressures.
• Fact: The CPI is typically released with a lag of several weeks, and its calculation is based on a moving average of price changes over several months, which can make it a less-than-ideal indicator of current inflation trends, as noted by Friedman, who argued that monetary policy should focus on forward-looking indicators of inflation.
• Source of confusion: The CPI's lag is often ignored in real-time economic analysis, which may rely too heavily on the index as a current indicator of inflation.
• Myth: The CPI is the only measure of inflation used by policymakers.
• Fact: Policymakers, such as those at the Federal Reserve, use a range of inflation indicators, including the GDP deflator and the personal consumption expenditures (PCE) price index, which can provide a more comprehensive picture of inflation trends, as noted by the Fed's use of the PCE price index as its preferred measure of inflation.
• Source of confusion: The dominance of the CPI in media reports can create the impression that it is the sole focus of policymakers.

Quick Reference

• Myth: CPI accurately reflects inflation rate for all households → Fact: CPI based on urban households, may not represent low-income households
• Myth: CPI is a perfect measure of inflation → Fact: CPI affected by substitution bias, as noted by Hicks
• Myth: CPI is calculated using a representative sample → Fact: CPI based on urban households, may not represent rural households
• Myth: CPI is adjusted for quality changes → Fact: CPI may not fully capture effects of rapid technological progress, such as Moore's Law
• Myth: CPI is a timely indicator of inflation → Fact: CPI released with a lag, based on moving average of price changes
• Myth: CPI is the only measure of inflation used by policymakers → Fact: Policymakers use range of indicators, including GDP deflator and PCE price index