You are here

Are Price Indexes Accurate Measures of Price-Level Changes?

25 April, 2016 - 09:12

Price indexes that employ fixed market baskets are likely to overstate inflation (and understate deflation) for four reasons:

  • Because the components of the market basket are fixed, the index does not incorporate consumer responses to changing relative prices.
  • A fixed basket excludes new goods and services.
  • Quality changes may not be completely accounted for in computing price-level changes.
  • The type of store in which consumers choose to shop can affect the prices they pay, and the price indexes do not reflect changes consumers have made in where they shop

To see how these factors can lead to inaccurate measures of price-level changes, suppose the price of chicken rises and the price of beef falls. The law of demand tells us that people will respond by consuming less chicken and more beef. But if we use a fixed market basket of goods and services in computing a price index, we will not be able to make these adjustments. The market basket holds constant the quantities of chicken and beef consumed. The importance in consumer budgets of the higher chicken price is thus overstated, while the importance of the lower beef price is understated. More generally, a fixed market basket will overstate the importance of items that rise in price and understate the importance of items that fall in price. This source of bias is referred to as the substitution bias.

The new-product bias, a second source of bias in price indexes, occurs because it takes time for new products to be incorporated into the market basket that makes up the CPI. A good introduced to the market after the basket has been defined will not, of course, be included in it. But a new good, once successfully introduced, is likely to fall in price. When VCRs were first introduced, for example, they generally cost more than $1,000. Within a few years, an equivalent machine cost less than $200. But when VCRs were introduced, the CPI was based on a market basket that had been defined in the early 1970s. There was no VCR in the basket, so the impact of this falling price was not reflected in the index. The DVD player was introduced into the CPI within a year of its availability.

A third price index bias, the quality-change bias, comes from improvements in the quality of goods and services. Suppose, for example, that Ford introduces a new car with better safety features and a smoother ride than its previous model. Suppose the old model cost $20,000 and the new modelcosts $24,000, a 20% increase in price. Should economists at the Bureau of Labor Statistics (BLS) simply record the new model as being 20% more expensive than the old one? Clearly, the new model is not the same product as the old model. BLS economists faced with such changes try to adjust for quality. To the extent that such adjustments understate quality change, they overstate any increase in the price level.

The fourth source of bias is called the outlet bias. Households can reduce some of the impact of rising prices by shopping at superstores or outlet stores (such as T.J. Maxx, Wal-Mart, or factory outlet stores), though this often means they get less customer service than at traditional department stores or at smaller retail stores. However, since such shopping has increased in recent years, it must be that for their customers, the reduction in prices has been more valuable to them than loss of service. Prior to 1998, the CPI did not account for a change in the number of households shopping at these newer kinds of stores in a timely manner, but the BLS now does quarterly surveys and updates its sample of stores much more frequently. Another form of this bias arises because the government data collectors do not collect price data on weekends and holidays, when many stores run sales.

Economists differ on the degree to which these biases result in inaccuracies in recording price-level changes. In late 1996, Michael Boskin, an economist at Stanford University, chaired a panel of economists appointed by the Senate Finance Committee to determine the magnitude of the problem in the United States. The panel reported that the CPI was overstating inflation in the United States by 0.8 to 1.6 percentage points per year. Their best estimate was 1.1 percentage points, as shown in the following Table 20.2. Since then, the Bureau of Labor Statistics has made a number of changes to correct for these sources of bias and since August 2002 has reported a new consumer price index called the Chained Consumer Price Index for all Urban Consumers (C-CPU-U) that attempts to provide a closer approximation to a “costof-living” index by utilizing expenditure data that reflect the substitutions that consumers make across item categories in response to changes in relative prices. However, a 2006 study by Robert Gordon, a professor at Northwestern University and a member of the original 1996 Boskin Commission, estimates that the total bias is still about 0.8 percentage points per year, as also shown in the Table 20.2.

The Boskin Commission reported that the CPI overstates the rate of inflation by 0.8 to 1.6 percentage points due to the biases shown, with a best-guess estimate of 1.1. A 2006 study by Robert Gordon estimates that the bias fell but is still about 0.8 percentage points.

Table 20.2 Estimates of Bias in the Consumer Price Index

Sources of Bias

1997 Estimate

2006 Estimate

Substitution

0.4

0.4

New products and quality change

0.6

0.3

Switching to new outlets

0.1

0.1

Total

1.1

0.8

Plausible range

0.8 – 1.6

---

 

Source: Robert J. Gordon, “The Boskin Commission Report: A Retrospective One Decade Later” (National Bureau of Economic Research Working Paper 12311, June 2006), available at http://www.nber.org/papers/w12311.

These findings of upward bias have enormous practical significance. With annual inflation running below 2% in three out of the last 10 years and averaging 2.7% over the 10 years, it means that the United States has come close to achieving price stability for almost a decade.

To the extent that the computation of price indexes overstates the rate of inflation, then the use of price indexes to correct nominal values results in an understatement of gains in real incomes. For example, average nominal hourly earnings of U.S. production workers were $13.01 in 1998 and $17.42 in 2007. Adjusting for CPI-measured inflation, the average real hourly earnings was $7.98 in 1998 and $8.40 in 2007, suggesting that real wages rose about 5.3% over the period. If inflation was overstated by 0.8% per year over that entire period, as suggested by Gordon’s updating of the Boskin Commission’s best estimate, then, adjusting for this overstatement, real wages should have been reported as $7.98 for 1998 and $9.01 for 2007, a gain of nearly 13%.

Also, because the CPI is used as the basis for calculating U.S. government payments for programs such as Social Security and for adjusting tax brackets, this price index affects the government’s budget balance, the difference between government revenues and government expenditures. The Congressional Budget Office has estimated that correcting the biases in the index would have increased revenue by $2 billion and reduced outlays by $4 billion in 1997. By 2007, the U.S. government’s budget would have had an additional $140 billion if the bias were removed.

KEY TAKEAWAYS

  • Inflation is an increase in the average level of prices, and deflation is a decrease in the average level of prices. The rate of inflation or deflation is the percentage rate of change in a price index.
  • The consumer price index (CPI) is the most widely used price index in the United States. Nominal values can be converted to real values by dividing by a price index.
  • Inflation and deflation affect the real value of money, of future obligations measured in money, and of fixed incomes. Unanticipated inflation and deflation create uncertainty about the future.
  • Economists generally agree that the CPI and other price indexes that employ fixed market baskets of goods and services do not accurately measure price-level changes. Biases include the substitution bias, the new-product bias, the quality-change bias, and the outlet bias.

TRY IT!

Suppose that nominal GDP is $10 trillion in 2003 and $11 trillion in 2004, and that the implicit price deflator has gone from 1.063 in 2003 to 1.091 in 2004. Compute real GDP in 2003 and 2004. Using the percentage change in the implicit price deflator as the gauge, what was the inflation rate over the period?

Case in Point: Take Me Out to the Ball Game …

The cost of a trip to the old ball game jumped 7.9% in 2008, according to Team Marketing Report, a Chicagobased newsletter. The report bases its estimate on its fan price index, whose market basket includes two adult average-priced tickets, two child average-priced tickets, two small draft beers, four small soft drinks, four regular-sized hot dogs, parking for one car, two game programs, and two least expensive, adult-sized adjustable baseball caps. The average price of the market basket was $191.92 in 2008.

Team Marketing compiles the cost of the basket for each of major league baseball’s 30 teams. According to thiscompilation, the Boston Red Sox was the most expensive team to watch in 2008; the Tampa Bay Rays was the Cheapest. The Rays made it to the World Series in 2008; the Red Sox did not. By that measure, the Rays were something of a bargain. The table shows the cost of the fan price index market basket for 2008.

Table 20.3

Team

Basket Cost

Team

Basket Cost

Boston Red Sox

$320.71

San Francisco

Giants

$183.74

New York

Yankees

$275.10

Cincinnati Reds

$167.14

Chicago Cubs

$251.96

Minnesota Twins

$165.71

New York Mets

$251.19

Baltimore Orioles

$165.40

Toronto Blue Jays

$230.46

Florida Marlins

$164.26

Los Angeles

Dodgers

$229.14

AZ

Diamondbacks

$162.84

St. Louis

Cardinals

$217.28

Colorado Rockies

$160.00

Houston Astros

$215.45

Atlanta Braves

$157.15

Chicago White

Sox

$214.51

Kansas City

Royals

$151.16

Oakland Athletics

$206.80

Texas Rangers

$148.04

San Diego Padres

$201.72

Pittsburgh Pirates

$146.32

Philadelphia

Phillies

$199356

Milwaukee

Brewers

$141.52

Washington

Nationals

$195.50

Los Angeles

Angels

$140.42

Cleveland Indians

$192.38

Tampa Bay Rays

$136.31

Seattle Mariners

$191.16

MLB Average

$191.92

Detroit Tigers

$190.13

   
 


Sources: Team Marketing Report, TMR’s Fan Cost Index Major League Baseball 2008 at http://www.teammarketing.com and personal interview.

ANSWER TO TRY IT! PROBLEM

Rearranging Equation 20.3, real GDP = nominal GDP/implicit price deflator. Therefore,

            Real GDP in 2003 = $10 trillion. / 1.063 = $9.4 trillion.

            Real GDP in 2004 = $11 trillion / 1.091 = $10.1 trillion.


Thus, in this economy in real terms, GDP has grown by $0.7 trillion.

To find the rate of inflation, we refer to Equation 20.4, and we calculate:

            Inflation rate in 2004 = (1.091 − 1.063) / 1.063 = 0.026 = 2.6 %

Thus, the price level rose 2.6% between 2003 and 2004.