The Data of Macroeconomics

Learning objectives
In this chapter, you will learn about:
Gross Domestic Product (GDP)
the Consumer Price Index (CPI)
the Unemployment Rate

Gross Domestic Product
Two definitions:
Total expenditure on
domestically-produced
final goods and services
Total income earned by
domestically-located
factors of production

Why expenditure = income
In every transaction,
the buyer’s expenditure becomes the seller’s income.
Thus, the sum of all expenditure equals
the sum of all income.

The Circular Flow

Value added
definition:
A firm’s value added is
the value of its output minus
the value of the intermediate goods
the firm used to produce that output.

Exercise: (Problem 2, p.38)
A farmer grows a bushel of wheat
and sells it to a miller for $1.00.
The miller turns the wheat into flour
and sells it to a baker for $3.00.
The baker uses the flour to make a loaf of
bread and sells it to an engineer for $6.00.
The engineer eats the bread.
Compute
value added at each stage of production
GDP

Final goods, value added, and GDP
GDP = value of final goods produced
= sum of value added at all stages of production
The value of the final goods already includes the value of the intermediate goods,
so including intermediate goods in GDP would be double-counting.

The expenditure components of GDP
consumption
investment
government spending
net exports

Consumption (C)
durable goods
last a long time
ex: cars, home appliances
non-durable goods
last a short time
ex: food, clothing
services
work done for consumers
ex: dry cleaning,
air travel.
def: the value of all goods and services bought by households. Includes:

U.S. Consumption, 2003

Investment (I)
def1: spending on [the factor of production] capital.
def2: spending on goods bought for future use.
Includes:
business fixed investment
spending on plant and equipment that firms will use to produce other goods & services
residential fixed investment
spending on housing units by consumers and landlords
inventory investment
the change in the value of all firms’ inventories

U.S. Investment, 2003

Investment vs. Capital
Capital is one of the factors of production.
At any given moment, the economy has a certain overall stock of capital.
Investment is spending on new capital.

Investment vs. Capital
Example (assumes no depreciation):
1/1/2004:
economy has $500b worth of capital
during 2004:
investment = $37b
1/1/2005:
economy will have $537b worth of capital

Stocks vs. Flows
A flow is a quantity measured per unit time. “U.S. investment was $1.6 trillion in 2001.”
A stock is a quantity
measured at a point
in time.
We might say
“the U.S. capital stock was $25.4 trillion as of December 6, 2003.”
FYI: “Flow” means the same thing as “rate”

Stocks vs. Flows - examples
stock flow
a person’s wealth a person’s annual saving
# of people with # of new college
college degrees graduates
the govt. debt the govt. budget deficit

Now you try:
Stock or flow?
The balance on your credit card statement.
How much you study economics outside of class.
The size of your compact disc collection.
The inflation rate.
The unemployment rate.

Government spending (G)
G includes all government spending on goods and services.
G excludes transfer payments
(e.g. unemployment insurance payments), because they do not represent spending on goods and services.

Government spending, 2003

Net exports (NX = EX - IM)
def: the value of total exports (EX)
minus the value of total imports (IM)

An important identity
Y = C + I + G + NX
where Y = GDP = the value of total output
C + I + G + NX = aggregate expenditure

A question for you:
Suppose a firm
produces $10 million worth of final goods
but only sells $9 million worth.
Does this violate the
expenditure = output identity?

Why output = expenditure
Unsold output goes into inventory,
and is counted as “inventory investment”…
…whether the inventory buildup was intentional or not.
In effect, we are assuming that
firms purchase their unsold output.

GDP:
An important and versatile concept
We have now seen that GDP measures
total income
total output
total expenditure
the sum of value-added at all stages
in the production of final goods

GNP vs. GDP
Gross National Product (GNP):
total income earned by the nation’s factors of production, regardless of where located
Gross Domestic Product (GDP):
total income earned by domestically-located factors of production, regardless of nationality.
(GNP – GDP) = (factor payments from abroad) – (factor payments to abroad)

Discussion Question:
In your country,
which would you want
to be bigger, GDP or GNP?
Why?

(GNP – GDP) as a percentage of GDP
selected countries, 2002

Real vs. Nominal GDP
GDP is the value of all final goods and services produced.
Nominal GDP measures these values using current prices.
Real GDP measure these values using the prices of a base year.

Real GDP controls for inflation
Changes in nominal GDP can be due to:
changes in prices
changes in quantities of output produced
Changes in real GDP can only be due to changes in quantities,
because real GDP is constructed using
constant base-year prices.

Practice problem, part 1
Compute nominal GDP in each year
Compute real GDP in each year using 2002 as the base year.

Answers to practice problem, part 1
Nominal GDP multiply Ps & Qs from same year
2002: $46,200 = $30 × 900 + $100 × 192
2003: $51,400
2004: $58,300
Real GDP multiply each year’s Qs by 2002 Ps
2002: $46,200
2003: $50,000
2004: $52,000 = $30 × 1050 + $100 × 205

U.S. Real & Nominal GDP, 1970-2004

GDP Deflator
The inflation rate is the percentage increase in the overall level of prices.
One measure of the price level is
the GDP Deflator, defined as

Practice problem, part 2
Use your previous answers to compute
the GDP deflator in each year.
Use GDP deflator to compute the inflation rate from 2002 to 2003, and from 2003 to 2004.

Answers to practice problem, part 2

Understanding the GDP deflator
Example with 3 goods
For good i = 1, 2, 3
Pit = the market price of good i in month t
Qit = the quantity of good i produced in month t
NGDPt = Nominal GDP in month t
RGDPt = Real GDP in month t

Understanding the GDP deflator
The GDP deflator is a weighted average of prices.
The weight on each price reflects
that good’s relative importance in GDP.
Note that the weights change over time.

Working with percentage changes
EX: If your hourly wage rises 5%
and you work 7% more hours,
then your wage income rises approximately 12%.
USEFUL TRICK #1 For any variables X and Y,
the percentage change in (X × Y )
≈ the percentage change in X
+ the percentage change in Y

Working with percentage changes
EX: GDP deflator = 100 × NGDP/RGDP.
If NGDP rises 9% and RGDP rises 4%,
then the inflation rate is approximately 5%.
USEFUL TRICK #2
the percentage change in (X/Y )
≈ the percentage change in X
− the percentage change in Y

Chain-weighted Real GDP
Over time, relative prices change, so the base year should be updated periodically.
In essence, “chain-weighted Real GDP” updates the base year every year.
This makes chain-weighted GDP more accurate than constant-price GDP.
But the two measures are highly correlated, and constant-price real GDP is easier to compute…
…so we’ll usually use constant-price real GDP.

Consumer Price Index (CPI)
A measure of the overall level of prices
Published by the Bureau of Labor Statistics (BLS)
Used to
track changes in the
typical household’s cost of living
adjust many contracts for inflation
(i.e. “COLAs”)
allow comparisons of dollar figures from different years

How the BLS constructs the CPI
Survey consumers to determine composition of the typical consumer’s “basket” of goods.
Every month, collect data on prices of all items in the basket; compute cost of basket
CPI in any month equals

Exercise: Compute the CPI
The basket contains 20 pizzas and
10 compact discs.
prices:
pizza CDs
2002 $10 $15
2003 $11 $15
2004 $12 $16
2005 $13 $15
For each year, compute
the cost of the basket
the CPI (use 2002 as the base year)
the inflation rate from the preceding year

cost of inflation
basket CPI rate
2002 $350 100.0 n.a.
2003 370 105.7 5.7%
2004 400 114.3 8.1%
2005 410 117.1 2.5%
answers:

The composition of the CPI’s “basket”

Understanding the CPI
Example with 3 goods
For good i = 1, 2, 3
Ci = the amount of good i in the CPI’s basket
Pit = the price of good i in month t
Et = the cost of the CPI basket in month t
Eb = cost of the basket in the base period

Understanding the CPI
The CPI is a weighted average of prices.
The weight on each price reflects
that good’s relative importance in the CPI’s basket.
Note that the weights remain fixed over time.

Reasons why
the CPI may overstate inflation
Substitution bias: The CPI uses fixed weights,
so it cannot reflect consumers’ ability to substitute toward goods whose relative prices have fallen.
Introduction of new goods: The introduction of new goods makes consumers better off and, in effect, increases the real value of the dollar. But it does not reduce the CPI, because the CPI uses fixed weights.
Unmeasured changes in quality:
Quality improvements increase the value of the dollar, but are often not fully measured.

The CPI’s bias
The Boskin Panel’s “best estimate”:
The CPI overstates the true increase in the cost of living by 1.1% per year.
Result: the BLS has refined the way it calculates the CPI to reduce the bias.
It is now believed that the CPI’s bias is slightly less than 1% per year.

Discussion topic:
If your grandmother receives Social Security, how is she affected by the CPI’s bias?
Where does the government get the money to pay COLAs to Social Security recipients?
If you pay income taxes and Social Security taxes, how does the CPI’s bias affect you?
Is the government giving your grandmother too big of a COLA?
How does your grandmother’s “basket” differ from the CPI’s?

CPI vs. GDP deflator
prices of capital goods
included in GDP deflator (if produced domestically)
excluded from CPI
prices of imported consumer goods
included in CPI
excluded from GDP deflator
the basket of goods
CPI: fixed
GDP deflator: changes every year

Two measures of inflation

Categories of the population
employed
working at a paid job
unemployed
not employed but looking for a job
labor force
the amount of labor available for producing goods and services; all employed plus unemployed persons
not in the labor force
not employed, not looking for work.

Two important labor force concepts
unemployment rate
percentage of the labor force that is unemployed
labor force participation rate
the fraction of the adult population
that ‘participates’ in the labor force

Exercise: Compute labor force statistics
U.S. adult population by group, May 2004
Number employed = 138.8 million
Number unemployed = 8.2 million
Adult population = 223.0 million
Use the above data to calculate
the labor force
the number of people not in the labor force
the labor force participation rate
the unemployment rate

Answers:
data: E = 138.8, U = 8.2, POP = 223.0
labor force
L = E +U = 138.8 + 8.2 = 147.0
not in labor force
NILF = POP – L = 223 – 147 = 76
unemployment rate
U/L = 8.2/147 = 0.056 or 5.6%
labor force participation rate
L/POP = 147/223 = 0.659 or 65.9%

Exercise: Compute percentage changes in labor force statistics
Suppose
the population increases by 1%
the labor force increases by 3%
the number of unemployed persons increases by 2%
Compute the percentage changes in
the labor force participation rate:
the unemployment rate:
2%
−1%

Employed workers help produce GDP, while unemployed workers do not.
So one would expect
a negative relationship between unemployment and real GDP.
This relationship is clear in the data…
Okun’s Law

Okun’s Law
1951
1984
1999
2000
1993
1982
1975
Change in
unemployment rate
10
Percentage change
in real GDP
Okun’s Law states that a one-percent decrease in unemployment is associated with two percentage points of additional growth in real GDP

Chapter Summary
Gross Domestic Product (GDP) measures both total income and total expenditure on the economy’s output of goods & services.
Nominal GDP values output at current prices; real GDP values output at constant prices. Changes in output affect both measures, but changes in prices only affect nominal GDP.
GDP is the sum of consumption, investment, government purchases, and net exports.

Chapter Summary
The overall level of prices can be measured by either
the Consumer Price Index (CPI),
the price of a fixed basket of goods purchased by the typical consumer
the GDP deflator,
the ratio of nominal to real GDP
The unemployment rate is the fraction of the labor force that is not employed.
When unemployment rises, the growth rate of real GDP falls.