Principles of

Economics W
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Measuring the
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CHAPTER
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24
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Cost of Living
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 In this chapter,
look for the answers to these questions

• What is the Consumer Price Index (CPI)?

How is it calculated? What’s it used for?
• What are the problems with the CPI? How
serious are they?
• How does the CPI differ from the GDP deflator?
• How can we use the CPI to compare dollar
amounts from different years? Why would we
want to do this, anyway?
• How can we correct interest rates for inflation?
 0

The Consumer Price Index (CPI)

● Measures the typical consumer’s cost of living

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 0

How the CPI Is Calculated

• Fix the “basket.”
The Bureau of Labor Statistics (BLS) surveys
consumers to determine what’s in the typical
consumer’s “shopping basket.”
• Find the prices.
The BLS collects data on the prices of all the
goods in the basket.
• Compute the basket’s cost.
Use the prices to compute the total cost of the
basket.
 0

How the CPI Is Calculated

• Choose a base year and compute the
index.
The CPI
LI in any year equals
cost of basket in current year
100 x
cost of basket in base year

•
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Compute the inflation rate.
~
% 0 of CPI

The percentage change in the CPI from the

preceding period.
Inflation CPI this year – CPI last year
= x 100%
rate CPI last year
EXAMPLE Basket: {4 pizzas, 10 lattes}
0

price of price of
year cost of basket
pizza latte
2010 $10 $2.00 $10 x 4 + $2 x 10 = $60
2011 $11 $2.50 $11 x 4 + $2.5 x 10 = $69
2012 $12 $3.00 $12 x 4 + $3 x 10 = $78

Compute CPI in each year using 2010 base year:

2010: 100 x ($60/$60) = 100 115 – 100 x 100%
15% =
2011: 100 x ($69/$60) = 115 100
2012: 100 x ($78/$60) = 130 130 – 115 x 100%
13% =
115
ACTIVE LEARNING 1 price price of
Calculate
CPI basket: the CPI of beef chicken
{10 beef,
2010 $4 $4
20 chicken}
2011 $5 $5
The CPI basket cost $120
in 2010, the base year. 2012 $9 $6

A. Compute the CPI in 2011.

B. What was the CPI inflation rate from 2011–
2012?
ACTIVE LEARNING 1 price price of
Answers
CPI basket: of beef chicken
{10 beef,
2010 $4 $4
20 chicken}
2011 $5 $5
The CPI basket cost $120
in 2010, the base year. 2012 $9 $6

A. Compute the CPI in 2011:

Cost of CPI basket in 2011
= ($5 x 10) + ($5 x 20) = $150
CPI in 2011 = 100 x ($150/$120) = 125
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 2 : Put

ACTIVE LEARNING 1 price price of

Answers
CPI basket: of beef chicken
{10 lbs beef,
2010 $4 $4
20 lbs chicken}
2011 $5 $5
The CPI basket cost $120
in 2010, the base year. 2012 $9 $6

B. What was the inflation rate from 2011–2012?

Cost of CPI basket in 2012
= ($9 x 10) + ($6 x 20) = $210
CPI in 2012 = 100 x ($210/$120) = 175
CPI inflation rate = (175 – 125)/125 = 40%
What’s in the CPI’s Basket?
ACTIVE LEARNING 2
Substitution
CPI basket: bias chicke cost of CPI
{10 beef, beef
n basket
20 chicken}
2010 $4 $4 $120
In 2010 and 2011,
households 2011 $5 $5 $150
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bought CPI basket. 2012
$9 $6 $210
In 2012, households bought {5 beef, 25 chicken}.

A. Compute cost of the 2012 household basket.

B. Compute % increase in cost of household
basket over 2011–12, compare to CPI inflation
rate.
ACTIVE LEARNING 2
Answers
CPI basket:
chicke cost of CPI
{10 beef, beef
n basket
20 chicken}
Household 2010 $4 $4 $120
basket in 2012: 2011 $5 $5 $150
{5 beef, 2012 $9 $6 $210
25 chicken}

A. Compute cost of the 2012 household basket.

($9 x 5) + ($6 x 25) = $195
ACTIVE LEARNING 2
Answers
CPI basket:
chicke cost of CPI
{10 beef, beef
n basket
20 chicken}
Household 2010 $4 $4 $120
basket in 2012: 2011 $5 $5 $150
{5 beef, 2012 $9 $6 $210
25 chicken}

B. Compute % increase in cost of household

basket over 2011–12, compare to CPI inflation
rate.
Rate of increase: ($195 – $150)/$150 = 30%
CPI inflation rate from previous problem = 40%
 Problems with the CPI: 0

Substitution Bias
S
● Over time, some prices rise faster than others.
Ent
● Consumers substitute toward goods that become
-
relatively cheaper, mitigating the effects of price
increases.(0) FE,
● The CPI misses this substitution because it uses
a fixed basket of goods.
● Thus, the CPI overstates increases in the cost of
living.
 Problems with the CPI: 0

Introduction of New Goods

● The introduction of new goods increases variety,

allows consumers to find products that more
closely meet their needs.
● In effect, dollars become more valuable.
● The CPI misses this effect because it uses a
fixed basket of goods.
● Thus, the CPI overstates increases in the cost
of living.
money Value > cust of
living
-

same i)
 Problems with the CPI: 0

Unmeasured Quality Change

● Improvements in the quality of goods in the

basket increase the value of each dollar.
● The BLS tries to account for quality changes
but probably misses some, as quality is hard to
measure.
● Thus, the CPI overstates increases in the cost of
living.
 0

Problems with the CPI

● Each of these problems causes the CPI to

overstate cost of living increases.
● The BLS has made technical adjustments,
but the CPI probably still overstates inflation
by about 0.5 percent per year.
Two Measures of Inflation smaller
0

imported good >

-
effect
oil price was

on GDP = GDP delfator inflation rate shallen

&
(
 Contrasting the CPI and GDP Deflator
0

Imported consumer goods: M

● included in CPI C (include m)
● excluded from GDP deflator M =

Capital goods:
● excluded from CPI
● included in GDP deflator I
(if produced domestically)
The basket:
● CPI uses fixed basket
● GDP deflator uses basket of
currently produced goods & services
ACTIVE LEARNING 3
CPI
In eachvs. GDPdetermine
scenario, deflator the effects on the
CPI and the GDP deflator.
C Ben't
A. Starbucks raises the price of Frappuccinos.
IP EDpp
B. Caterpillar raises the price of the industrial
tractors it manufactures at its Illinois factory.
C. Armani raises the price of the Italian jeans it
sells in the U.S. mi >
-

(Pip
(In U S
.)
.
ACTIVE LEARNING 3
Answers
A. Starbucks raises the price of Frappuccinos.
The CPI and GDP deflator both rise.
B. Caterpillar raises the price of the industrial
tractors it manufactures at its Illinois factory.
The GDP deflator rises, the CPI does not.
C. Armani raises the price of the Italian jeans it
sells in the U.S.
The CPI rises, the GDP deflator does not.
 0
Correcting Variables for Inflation:
Comparing Dollar Figures from Different Times
● Inflation makes it harder to compare dollar
amounts from different times.
● Example: the minimum wage
● $1.25 in Dec 1963
● $7.25 in Dec 2013
● Did min wage have more purchasing power in
Dec 1963 or Dec 2013?
● To compare, use CPI to convert 1963 figure into
“2013 dollars”…
 YP F
Pix
=

0
Correcting Variables for Inflation: InPn Is no
Comparing Dollar Figures from Different Times
Amount Amount Price level today
in today’s = in year T x
dollars dollars Price level in year T
0

● In our example,
● “year T ” is 12/1963, “today” is 12/2013
● Min wage was $1.25 in year T
● CPI = 30.9 in year T, CPI = 234.6 today

The minimum wage 234.6

in 1963 was $9.49 $9.49 = $1.25 x
30.9
in 2013 dollars. Yi In
Ynin 7 IS
1. T was
higher = .
The U.S. Minimum Wage in Current Dollars
and Today’s Dollars, 1960–2013

2013 dollars

10

current dollars
0
2,000
 Correcting Variables for Inflation: 0

Real vs. Nominal Interest Rates

The nominal interest rate:
● the interest rate not corrected for inflation
● the rate of growth in the dollar value of a
deposit or debt
The real interest rate:
● corrected for inflation
● the rate of growth in the purchasing power of a
deposit or debt
Real interest rate
= (nominal interest rate) – (inflation rate)
 0
Correcting Variables for Inflation:
Real vs. Nominal Interest Rates
Example:
● Deposit $1,000 for one year.
● Nominal interest rate is 9%.
● During that year, inflation is 3.5%.
● Real interest rate
= Nominal interest rate – Inflation
= 9.0% – 3.5% = 5.5%
● The purchasing power of the $1000 deposit
has grown 5.5%.
 Real and Nominal Interest Rates in the U.S., 0
1950–2013

10

-10
2,000

Real Nominal
Summary

• The Consumer Price Index is a measure of the

cost of living. The CPI tracks the cost of the
typical consumer’s “basket” of goods & services.

• The CPI is used to make Cost of Living

Adjustments and to correct economic variables
for the effects of inflation.
• The real interest rate is corrected for inflation
and is computed by subtracting the inflation rate
from the nominal interest rate.
Question 1
CPI
=be a - 0

In a simple economy, people consume only 2 goods, food

and clothing. The market basket of goods used to compute
the CPI consists of 50 units of food and 10 units of clothing
Food Clothing
300

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2002 price per unit $4 $10 CPI1

2003 price per unit $6 $20 Sug

EPI g
● (a) What are the percentage increases in the price of
food and in the price of clothing? = wit
● (b) What is the percentage increase in the CPI? to
66 7
● (c) Do these price changes affect all consumers to the
=
.
%
same extent? Explain. CT > Pot (Worse the
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P of #
 0

Question 2
Jay and Joyce meet George, the banker, to work out the
details of a mortgage. They all expect that inflation will be
2 percent over the term of theO loan, and they agree on a
nominal interest rate of 6 percent. As it turns out, the
inflation rate is 5 percent over the term of the loan.
0 -2
● (a) What was the expected real interest rate? = 4
● (b) What was the actual real interest rate? 0
-5 =
1

● (c) Who benefited and who lost because of the

unexpected inflation?
: UAE j
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