© 2013 Pearson
Which movie really was
the biggest box office hit?
© 2013 Pearson
23
The CPI and the Cost of Living
CHAPTER CHECKLIST
When you have completed your
study of this chapter, you will be able to
1 Explain what the Consumer Price Index (CPI) is and
how it is calculated.
2 Explain the limitations of the CPI and describe other
measures of the price level.
3 Adjust money values for inflation and calculate real
wage rates and real interest rates.
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23.1 THE CONSUMER PRICE INDEX
Consumer Price Index (CPI) is a measure of the
average of the prices paid by urban consumers for a
fixed market basket of consumer goods and services.
The BLS calculates the CPI every month.
We can use these numbers to compare what a fixed
basket of goods costs this month with what it cost in
some previous month.
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23.1 THE CONSUMER PRICE INDEX
Reading the CPI Numbers
The CPI is defined to equal 100 for a period called the
reference base period.
Reference base period is a period for which the CPI
is defined to equal 100.
Currently, the reference base period is 19821984.
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23.1 THE CONSUMER PRICE INDEX
In July 2011, the CPI was 225.4.
The average of the prices paid by urban consumers for
a fixed market basket of consumer goods and services
was 125.4 percent higher in July 2011 than it was on
the average during 19821984.
In June 2011, the CPI was 224.3.
The average of the prices paid by urban consumers for
a fixed market basket of consumer goods and services
increased by 1.1 of a percentage point in July 2011.
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23.1 THE CONSUMER PRICE INDEX
Constructing the CPI
Three stages:
• Selecting the CPI basket
• Conducting the monthly price survey
• Calculating the CPI
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23.1 THE CONSUMER PRICE INDEX
The CPI Market Basket
Make the relative importance of the items in the CPI
basket the same as in the budget of an average urban
household.
The CPI is calculated each month, but the CPI basket is
not updated each month.
The CPI basket in 2011 is based on information
obtained from the Consumer Expenditure Surveys
conducted during 2007 and 2008.
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23.1 THE CONSUMER PRICE INDEX
Figure 23.1 shows the CPI basket in July 2011.
This shopping cart is filled with the items that an average
household buys.
23.1 THE CONSUMER PRICE INDEX
The Monthly Price Survey
Each month, BLS employees check the prices of the
80,000 goods and services in the CPI basket in 30
metropolitan areas.
Because the CPI measures price changes, it is
important that the prices recorded refer to exactly the
same items.
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23.1 THE CONSUMER PRICE INDEX
Calculating the CPI
The CPI calculation has three steps:
• Find the cost of the CPI basket at base period
prices.
• Find the cost of the CPI basket at current period
prices.
• Calculate the CPI for the base period and the
current period.
Table 23.1 on the next slide shows a simplified CPI
calculation in which we assume a base period of 2005.
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23.1 THE CONSUMER PRICE INDEX
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23.1 THE CONSUMER PRICE INDEX
CPI =
Cost of CPI basket at current period prices
x 100
Cost of CPI basket at base period prices
For 2005, the CPI is:
For 2012, the CPI is:
© 2013 Pearson
$50
x 100 = 100
$50
$70
$50
x 100 = 140
23.1 THE CONSUMER PRICE INDEX
Measuring Inflation and Deflation
Inflation rate is the percentage change in the price
level from one year to the next.
CPI in current year  CPI in previous year x 100
Inflation rate =
CPI in previous year
140  120 x 100 = 16.7 percent
Inflation rate =
120
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23.1 THE CONSUMER PRICE INDEX
Deflation is a situation in which the inflation rate is
negative.
For example, in July 2009 the CPI was 214.8, and in
July 2008 it was 219.1
So during that year,
214.8  219.1 x 100 = 2.0 percent.
Inflation rate =
219.1
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23.1 THE CONSUMER PRICE INDEX
Figure 23.2 shows the CPI in part (a) and the inflation rate
in part (b).
23.1 THE CONSUMER PRICE INDEX
1. The price level was rising rapidly in the 1980s and the
inflation rate was high.
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23.1 THE CONSUMER PRICE INDEX
2. The price level was rising slowly during the 1990s and
2000s and the inflation rate was low.
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23.1 THE CONSUMER PRICE INDEX
3. In 2009, the price level fell and the inflation rate was
negative.
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23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
Cost of living index is a measure of changes in the
amount of money that people would need to spend to
achieve a given standard of living.
The CPI does not measure the cost of living because
• It does not measure all the components of the cost
of living
• Some components are not measured exactly
So the CPI is possibly a biased measure.
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23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
 Sources of Bias in the CPI
The potential sources of bias in the CPI are
•
•
•
•
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New goods bias
Quality change bias
Commodity substitution bias
Outlet substitution bias
23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
New Goods Bias
• New goods do a better job than the old goods that
they replace, but cost more.
• The arrival of new goods puts an upward bias into
the CPI and its measure of the inflation rate.
Quality Change Bias
• Better cars and televisions cost more than the
versions they replace.
• A price rise that is a payment for improved quality
is not inflation but might get measured as inflation.
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23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
Commodity Substitution Bias
• If the price of beef rises faster than the price of
chicken, people buy more chicken and less beef.
• The CPI basket doesn’t change to allow for the
effects of substitution between goods.
Outlet Substitution Bias
• If prices rise more rapidly, people use discount
stores more frequently.
• The CPI basket doesn’t change to allow for the
effects of outlet substitution.
© 2013 Pearson
23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
 The Magnitude of the Bias
The Boskin Commission estimated the bias to be 1.1
percentage points per year.
If the measured inflation rate is 3.1 percent a year, most
likely the actual inflation rate is 2.0 percent a year.
To reduce the bias, the BLS has decided to increase
the frequency of its Consumer Expenditure Survey and
revise the CPI basket every two years.
When the BLS revises the CPI basket, the reference
base period does not change.
© 2013 Pearson
23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
Two Consequences of the CPI Bias
Two main consequences of the bias in the CPI are
• Distortion of private contracts
• Increases in government outlays and decreases in
taxes
Distortion of Private Contracts
Many wage contracts are linked to the CPI.
If the CPI is biased, these contracts might deliver an
outcome different from that intended by the parties.
© 2013 Pearson
23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
Suppose that the UAW and GM sign a 3-year wage deal:
In the first year, the wage will be $30 an hour and will rise
by the inflation rate in the next two years.
If the inflation rate is 5 percent a year, the wage rises to
$31.50 an hour in the second year and $33.08 an hour in
the third year.
But if the actual inflation rate is 2 percent a year, the
intended wages in the second and third years are $30.90
an hour and $31.83 an hour.
The workers’ gain is GM’s loss. With thousands of workers,
GM’s loss would be millions of dollars over the 3 years.
© 2013 Pearson
23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
Increases in Government Outlays and Decreases in
Taxes
Close to a third of federal government outlays are linked
directly to the CPI.
The CPI is used to adjust
• 49 million Social Security benefit payments
• 27 million food stamp payments
• 4 million pensions for retired military personnel,
federal civil servants, and their surviving spouses
• the budget for 3 million school lunches
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23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
The CPI is used to adjust the income levels at which
higher tax rates apply.
Because tax rates on large incomes are higher than
those on small incomes as incomes rise, the burden of
taxes would rise relentlessly if these adjustments were
not made.
To the extent that the CPI is biased upward, the tax
adjustments over-compensate for rising prices and
decrease the amount paid in taxes.
© 2013 Pearson
23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
Alternative Measures of the Price Level and
Inflation Rate
Several alternative measures of the price level are
available.
Here we look at
• GDP price index
• Personal consumption expenditures (PCE) price index
• PCE price index excluding food and energy
© 2013 Pearson
23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
GDP Price Index
The GDP price index is an average of current prices
of all the goods and services included in GDP
expressed as a percentage of base-year prices.
GDP price index = (Nominal GDP  Real GDP)  100.
The GDP price index is a measure of the price level.
The percentage change in the GDP price index is a
measure of the inflation rate.
© 2013 Pearson
23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
Two differences between the GDP price index and the CPI
result in different estimates of the price level and inflation rate.
1. The GDP price index uses the prices of all the goods
and services in GDP.
The CPI uses prices of consumption goods and services.
2. The GDP price index weights each item using information
about current as well as past quantities.
In contrast, the CPI weights each item using information
from a past Consumer Expenditure Survey.
© 2013 Pearson
23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
Because the GDP price index uses information on
current year quantities, it includes new goods and
quality improvements and even allows for substitution
effects of both commodities and retail outlets.
So in principle, the GDP price index is not subject to the
biases of the CPI.
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23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
PCE Price Index
The PCE price index is an average of current prices
of all the goods and services included in the
consumption expenditure component of GDP expressed
as a percentage of base-year prices.
The PCE price index, like the GDP price index, uses
current information on quantities and prices and to
some degree overcomes the sources of bias in the CPI.
Because it focuses on consumption expenditure, it a
possible measure of the cost of living.
© 2013 Pearson
23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
PCE Price Index Excluding Food and Energy
Food and energy prices fluctuate much more than other
prices, so their changes can obscure the underlying
trends in prices.
By excluding these highly variable items, the underlying
price level and inflation trends can be seen more
clearly.
The percentage change in the PCE price index
excluding food and energy is called the core inflation
rate.
© 2013 Pearson
23.2 THE CPI AND OTHER PRICE LEVEL …
Figure 23.3 shows the three
measures of the price level and
their inflation rates.
The three measures of the price
level move together.
But the CPI increases more
quickly than the two PCE
measures.
The path of the CPI shows the
bias in the CPI as a measure of
the price level.
23.2 THE CPI AND OTHER PRICE LEVEL MEASURES
The three measures of the
inflation rate fluctuate together.
But the core inflation rate
fluctuates less than the other
two measures.
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23.3 NOMINAL AND REAL VALUES
Dollars and Cents at Different Dates
To compare dollar amounts at different dates,
we need to know the CPI at those dates.
Convert the price of a 2¢ stamp in 1911 into its
2011 equivalent:
Price of stamp in 2011 dollars =
Price of stamp in 1911 dollars x
CPI in 2011
CPI in 1911
225.4
= 46 cents
= 2¢ x
9.8
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23.3 NOMINAL AND REAL VALUES
Alternatively, we could convert the 44¢ stamp in 2011
into its 1911 equivalent by calculating the real price of
the 2011 stamp in 1911.
Price of stamp in 1911 dollars =
Price of stamp in 2011 dollars x
CPI in 1911
CPI in 2011
9.8
= 1.91 cents.
=44¢ x
225.4
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23.3 NOMINAL AND REAL VALUES
Nominal and Real Values in Macroeconomics
Macroeconomics makes a big issue of the distinction
between nominal values and real values:
• Nominal GDP and real GDP
• Nominal wage rate and real wage rate
• Nominal interest rate and real interest rate
We studied the distinction between and calculation of
nominal and real GDP in Chapter 21. Here, we’ll look at
the other two.
© 2013 Pearson
23.3 NOMINAL AND REAL VALUES
Nominal Wage Rate and Real Wage Rate
Nominal wage rate is the average hourly wage rate
measured in current dollars.
Real wage rate is the average hourly wage rate
measured in the dollars of a given reference base year.
© 2013 Pearson
23.3 NOMINAL AND REAL VALUES
To calculate the real hourly wage rate, we divide the
nominal hourly wage rate by the CPI and multiply by 100.
That is,
Nominal wage rate in 2011
Real wage rate in 2008 =
Real wage rate in 2008 =
CPI in 2011
$19.04
225.4
x 100 = $8.45
The $8.45 an hour is in 19821984 dollars.
© 2013 Pearson
x 100
23.3 NOMINAL AND REAL VALUES
Figure 23.4 shows
nominal and real wage
rates: 1981 to 2011.
Since 1981, the real
wage rate barely
changed,
despite the increase in
the nominal wage rate
every year.
23.3 NOMINAL AND REAL VALUES
Nominal Interest Rate and Real Interest Rate
Nominal interest rate is the dollar amount of interest
expressed as a percentage of the amount loaned.
Real interest rate is the goods and services forgone
in interest expressed as a percentage of the amount
loaned.
Real interest rate = Nominal interest rate – Inflation rate.
© 2013 Pearson
23.3 NOMINAL AND REAL VALUES
Figure 23.5 shows real
and nominal interest
rates: 1971 to 2011.
During the 1970s,
the real interest rate
became negative.
The nominal interest
rate increased during
the high-inflation 1980s.
Which Movie Really Was the Biggest
Box Office Hit?
We measure the changing value of money by using a price
index.
The most common price index is the CPI.
Because the CPI is biased, we supplement it with other
indexes and other information.
By using a price index, we can calculate the amount that a
movie really earns at the box office.
© 2013 Pearson
Which Movie Really Was the Biggest
Box Office Hit?
Gone with the Wind was made in 1939 and rereleased in
nine subsequent years.
By 2011, it had earned a total box office revenue of almost
$200 million in the United States.
Harry Potter and the Deathly Hallows, Part 2 was released
in 2011.
During the summer of 2011, it earned $366 million.
Harry Potter earned 1.83 times the dollars earned by Gone
with the Wind.
Which movie really earned the more box office revenue?
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Which Movie Really Was the Biggest
Box Office Hit?
To convert the Gone with the Wind revenues into 2011
dollars, …
multiply the dollars received each year by the 2011 CPI and
divide by the CPI for the year in which the dollars were
earned.
Box-Office Mojo has done such a calculation, but rather than
use the CPI, it used the average prices of movie tickets.
According to Box-Office Mojo, valuing the tickets for Gone
with the Wind at 2011 movie-ticket prices, it has earned
$1,620 million, about 4.4 times Harry Potter’s revenue.
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Which Movie Really Was the Biggest
Box Office Hit?
Because Box-Office Mojo uses average ticket prices, the
real variable that it compares is the number of tickets sold.
The average ticket price in 2011 was $7.96, so 204 million
movie-goers have seen Gone with the Wind and 46 million
have seen Harry Potter and the Deathly Hallows, Part 2.
© 2013 Pearson