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mankiw's macroeconomics modules. ®. A PowerPoint  Tutorial to Accompany macroeconomics, 5th ed. N. Gregory Mankiw Mannig J. Simidian. CHAPTER TWO The Data of Macroeconomics. GDP, CPI and Unemployment.

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mankiw's macroeconomics modules


A PowerPointTutorial

to Accompany macroeconomics, 5th ed.

N. Gregory Mankiw

Mannig J. Simidian


The Data of Macroeconomics

GDP, CPI and Unemployment

Gross Domestic Product (GDP) is the market value of all final goods and services produced within an economy in a given period of time.

The consumer price index (CPI) measures the level of prices.

The unemployment rate tells us the fraction of workers who are unemployed.

Income, Expenditure

And the Circular Flow

Total income of everyone in the economy

There are 2 ways

of viewing GDP

Total expenditure on the economy’s

output of goods and services

Income $





Expenditure $

For the economy as a whole, income must equal expenditure.

GDP measures the flow of dollars in this economy.



Rules for Computing GDP

1) To compute the total value of different goods and services, the national income accounts use market prices.

Thus, if

GDP = (Price of apples Quantity of apples)

+ (Price of oranges  Quantity of oranges)

= ($0.50  4) + ($1.00  3)

GDP = $5.00

2) Used goods are not included in the calculation of GDP.

3) The treatment of inventories depends on if the goods are stored or

if they spoil. If the goods are stored, their value is included in GDP.

If they spoil, GDP remains unchanged. When the goods are finally sold

out of inventory, they are considered used goods (and are not counted).

More Rules for Computing GDP

4) Intermediate goods are not counted in GDP– only the value of

final goods. Reason: the value of intermediate goods is already

included in the market price. Value addedof a firm equals the

value of the firm’s output less the value of the intermediate goods

the firm purchases.

5) Some goods are not sold in the marketplace and therefore don’t

have market prices. We must use their imputed value as an estimate

of their value. For example, home ownership and government services.

Real vs. Nominal GDP

The value of final goods and services measured at current prices is called nominal GDP. It can change over time either because there is a change in the amount (real value) of goods and services or a change in the prices of those goods and services.

Hence, nominal GDP Y = P  y, where P is the price level and y is real output– and remember we use output and GDP interchangeably.

Real GDP or, y = YP is the value of goods and services measured using a constant set of prices.

This distinction between real and nominal can also be applied to other monetary values, like wages. Nominal (or money) wages can be denoted by W and decomposed into a real value (w) and a price variable (P). Hence, W = nominal wage = P • w

w = real wage = w/P

This conversion from nominal to real units allows us to eliminate the problems created by having a measuring stick (dollar value) that essentially changes length over time, as the price level changes.

Let’s see how real GDP is computed in our apple and orange economy.

For example, if we wanted to compare output in 2002 and output in 2003, we would obtain base-year prices, such as 2002 prices.

Real GDP in 2002 would be:

(2002 Price of Apples 2002 Quantity of Apples) +

(2002 Price of Oranges  2002 Quantity of Oranges).

Real GDP in 2003 would be:

(2002 Price of Apples  2003 Quantity of Apples) +

(2002 Price of Oranges  2003 Quantity of Oranges).

Real GDP in 2004 would be:

(2002 Price of Apples  2004 Quantity of Apples) +

(2002 Price of Oranges  2004 Quantity of Oranges).

GDP Deflator = Nominal GDP

Real GDP

GDP Deflator

Nominal GDP measures the current dollar value of the output of

the economy.

Real GDP measures output valued at constant prices.

The GDP deflator, also called the implicit price deflator for GDP,

measures the price of output relative to its price in the base year. It

reflects what’s happening to the overall level of prices in the economy.

Chain-Weighted Measures of GDP

In some cases, it is misleading to use base year prices that

prevailed 10 or 20 years ago (i.e. computers and

college). In 1995, the Bureau of Economic Analysis

decided to use chain-weighted measures of

real GDP. The base year changes continuously

over time. This new chain-weighted measure is better than the more traditional measure because it ensures that prices will not be too out of date.

Average prices in 2001

and 2002 are used to measure

real growth from 2001 to 2002.

Average prices in 2002 and 2003

are used to measure real growth from

2002 to 2003 and so on. These growth

rates are united to form a chain that is

used to compare output between any two


Total demand

for domestic

output (GDP)


spending by

businesses and


is composed


Net exports

or net foreign



purchases of goods

and services


spending by


Components of Expenditure

Y = C + I + G + NX

This is the called the national income accounts identity.

Other Measures of Income

To see how the alternative measures of income relate to one

another, we start with GDP and add or subtract various quantities.

To obtain gross national product (GNP), we add receipts of factor

income (wages, profit, and rent) from the rest of the world and

subtract payments of factor income to the rest of the world.

GNP = GDP+Factor Payments from Abroad -Factor Payments to Abroad

Whereas GDP measures the total income produced domestically, GNP

measures the total income earned by nationals (residents of a nation).

To obtain net national product (NNP), we subtract the depreciation of

capital-- the amount of the economy’s stock of plants, equipment, and

residential structures that wears out during the year:

NNP = GNP - Depreciation

Computing the CPI

The Consumer Price Index (CPI) turns the prices of many goods and services into a single index measuring the overall level of prices.

Let’s see how the CPI would be computed in our

apple and orange economy.

For example, suppose that the typical consumer buys 5 apples and 2 oranges every month. Then the basket of goods consists of 5 apples and 2 oranges, and the CPI is:

CPI= ( 5  Current Price of Apples) + (2  Current Price of Oranges)

( 5  2002 Price of Apples) + (2  2002 Price of Oranges)

In this CPI calculation, 2002 is the base year. The index tells how much it costs to buy 5 apples and 2 oranges in the current year relative to how much it cost to buy the same basket of fruit in 2002.

CPI Versus the GDP Deflator

The GDP deflator measures the prices of all goods produced, whereas the CPI measures prices of only the goods and services bought by consumers. Thus, an increase in the price of goods bought by firms or the government will show up in the GDP deflator but not in the CPI.

Also, another difference is that the GDP deflator includes only those goods and services produced domestically. Imported goods are not a part of GDP and therefore don’t show up in the GDP deflator.

The final difference is the way the two aggregate the prices in the economy. The CPI assigns fixed weights to the prices of different goods, whereas the GDP deflator assigns changing weights.

Unemployment Rate = Number of Unemployed

Labor Force

 100

Labor-Force Participation Rate = Labor Force

Adult Population

 100

Measuring Unemployment

The labor force is defined as the sum of the employed and unemployed, and the unemployment rate is defined as the percentage of the labor force that is unemployed.

The labor force participation rateis the percentage of the adult population who are in the labor force.

Okun's Law

Okun's Law

The negative relationship between unemployment and GDP is called

Okun’s Law, after Arthur Okun, the economist who first studied it.

In short, it is defined as:

Percentage Change in Real GDP =

3% - 2  the Change in the Unemployment Rate

If the unemployment rate remains the same, real GDP grows by

about 3 percent. For every percentage point the unemployment rate

rises, real GDP growth typically falls by 2 percent. Hence, if the

unemployment rate rises from 6 to 8 percent, then real GDP growth

would be:

Percentage Change in Real GDP = 3% - 2  (8% - 6%) = - 1%

Key Concepts of Ch. 2

Gross domestic product (GDP) Consumer Price Index (CPI) Unemployment Rate National income accounting Stocks and flows Value added Imputed value Nominal versus real GDP GDP deflator

National income accounts identity Consumption Investment Government Purchases Net Exports Labor force Labor-force participation rate Okun’s Law