DP Economics SL 3.1 Measuring Economic Activity and Illustrating Its Variations

DP Economics SL 3.1 Measuring Economic Activity and Illustrating Its Variations - Full notes

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DP Economics SL | 3.1 Measuring Economic Activity and Illustrating Its Variations

DP ECONOMICS · UNIT 3: MACROECONOMICS

3.1

Measuring Economic Activity and Illustrating Its Variations

Full notes for SL · IB-style

Contents

1	The circular flow of income
2	Measuring national income: GDP and GNI
3	Nominal and real values, per capita and PPP
4	Limitations of GDP as a measure of well-being
5	Alternative measures of well-being
6	The business cycle and output gaps
7	Three methods of measuring national income
8	Avoiding double counting
9	GDP and GNI
10	Nominal and real GDP
11	GDP per capita
12	Purchasing power parity (PPP)
13	Limitations of GDP as a measure of well-being
14	Alternative measures of well-being
15	The business cycle
16	Output gaps
17	Green GDP
18	Mixed review: worked problems
19	Additional exam-style practice
20	Index numbers in macroeconomics
21	The informal economy
22	Comparing countries using data
23	Common misconceptions and links
24	Exam-style question with markscheme
25	Check your understanding
26	Summary and topic map

These are full teaching notes. Read each section in order, try the Think about it question before you read on, and do every Quick check before moving to the next section.

Before you start

Rate yourself on each statement now, and again after you've worked through the notes. Shade R (not yet), A (getting there) or G (confident).

I can…	R	A	G
explain the circular flow of income with leakages and injections
explain the output, income and expenditure methods of measuring GDP
distinguish GDP from GNI and calculate each
calculate real GDP using a price deflator, and GDP per capita
explain why PPP is used for international comparisons
evaluate GDP as a measure of well-being
explain alternative measures such as the OECD Better Life Index and the Happy Planet Index
draw and explain the business cycle, including output gaps

There is no additional HL content in 3.1. SL and HL students study the same material.

Guiding questions

How do we know whether an economy is growing? Does a higher GDP always mean people are better off? Why do economies go through booms and recessions?

How this topic is examined

3.1 provides the measurement tools for the whole of macroeconomics. Paper 2 frequently asks you to calculate GDP from components, real GDP from nominal GDP, growth rates or GDP per capita, and to explain the limitations of GDP using information in a text.

Paper 1 essays on growth or development often require you to evaluate GDP as a measure of well-being, and the business cycle diagram is used to explain recessions and output gaps.

Command term	What the examiner wants
Define	the precise meaning, ideally in the IB wording, in one or two sentences
Draw / Sketch	a fully labelled diagram with every axis, curve, equilibrium and change labelled
Explain	a causal chain linked to economic theory, usually supported by a diagram
Analyse	break a situation into its parts and trace the effects of each
Evaluate / Discuss	weigh up arguments, question assumptions and reach a justified conclusion using real-world examples
Calculate	show the formula, substitute values and state units ($ bn, %)

How to use these notes

Each section teaches one part of the syllabus in full. You'll see these boxes throughout; each has one job:

Box	What it's for
Think about it	a question to get you thinking before a section; the answer comes in the section
Key point	the one idea you must not forget
Common mistake	an error examiners see every year, and how to avoid it
In the real world	where the economics shows up outside the classroom
Try this	something quick you can do yourself to test the idea
Worked example	full solutions with IB-style marks (M1 method, A1 answer, R1 reasoning)
Quick check	short questions to test yourself at the end of each section

1 The circular flow of income

Income, output and spending are three views of the same flow.

Think about it

When you buy a book for $20, that $20 becomes someone else's income. Follow it: whose income, and what happens to it next?

Macroeconomics studies the economy as a whole, so we need a picture of how money moves through it. The circular flow of income model, first met in 1.1, provides it.

In the simplest model, households own the factors of production and sell their services to firms, receiving factor incomes (wages, rent, interest and profit). Firms use the factors to produce goods and services, which households buy with their income. Money flows from firms to households as income, and back from households to firms as spending. Goods, services and factor services flow in the opposite direction.

This gives the central identity of national accounting: national output = national income = national expenditure. Every dollar spent on a final good is received by someone as income, and every good produced is either bought or added to stocks, which counts as investment.

Figure 1. The simple circular flow of income between households and firms.

A real economy has three more sectors. Financial institutions take in household saving and lend it to firms for investment. The government collects taxes and makes government spending. The foreign sector buys our exports and sells us imports.

Saving, taxes and imports are leakages (withdrawals): income that does not flow back to domestic firms as spending. Investment, government spending and exports are injections: spending on domestic output that does not come from household consumption.

If injections exceed leakages, the circular flow grows and national income rises. If leakages exceed injections, national income falls. National income is in equilibrium when total leakages equal total injections: S + T + M = I + G + X.

Leakage	Injection	Sector
Saving (S)	Investment (I)	financial
Taxes (T)	Government spending (G)	government
Imports (M)	Exports (X)	foreign

Quick check

1. Why does national income equal national output?

2. List the three leakages and three injections.

3. What happens to national income if leakages exceed injections?

Answers: 1. every expenditure on output is someone's income 2. S, T, M; I, G, X 3. it falls

2 Measuring national income: GDP and GNI

Three methods, one answer.

2.1 Gross domestic product

Gross domestic product (GDP) is the total value of all final goods and services produced within a country's borders in a given period, usually a year or a quarter. 'Domestic' means within the country, whoever owns the factors. 'Final' means goods bought by their end user: counting intermediate goods (steel sold to a car maker) as well would double-count them.

Because of the circular flow, GDP can be measured in three ways, which in theory give the same answer.

The output method adds up the value of output produced by every industry, using value added at each stage of production to avoid double counting.

The income method adds up all the incomes earned from producing that output: wages, rent, interest and profit.

The expenditure method adds up all spending on final goods and services:

GDP = C + I + G + (X − M)

Component	Meaning
C: consumption	household spending on goods and services
I: investment	firms' spending on capital goods, plus changes in stocks
G: government spending	government spending on goods and services (not transfer payments)
X − M: net exports	exports minus imports

Notice that government spending in GDP excludes transfer payments such as pensions and unemployment benefits, because these are not payments for newly produced output; they are counted when the recipients spend them, as consumption.

2.2 Gross national income

Gross national income (GNI) measures the income earned by a country's residents and firms, wherever in the world it is earned. It equals GDP plus income earned by residents from abroad, minus income earned by foreigners in the country:

GNI = GDP + net income from abroad

For a country with many foreign-owned firms that send profits home, GNI is lower than GDP. Ireland is a famous example: its GDP is inflated by the profits of multinational companies, so its GNI is much lower. For a country with many workers abroad who send income home, GNI can exceed GDP.

WORKED EXAMPLE 1 GDP and GNI

An economy has C = $600 bn, I = $150 bn, G = $200 bn, X = $120 bn and M = $140 bn. Net income from abroad is −$25 bn. Calculate GDP and GNI.

Solution

GDP = 600 + 150 + 200 + (120 − 140)M1

= $930 bnA1

GNI = 930 + (−25) = $905 bnA1

Common mistake

Adding imports in the expenditure method. Imports are subtracted: spending on foreign goods is not domestic output.

Quick check

1. Define GDP.

2. Why are only final goods counted?

3. Write the expenditure equation.

4. When is GNI less than GDP?

Answers: 1. value of final goods and services produced within a country in a period 2. to avoid double counting 3. GDP = C + I + G + (X − M) 4. when foreigners earn more from the country than residents earn abroad

3 Nominal and real values, per capita and PPP

To compare over time and between countries, adjust for prices and population.

3.1 Nominal and real GDP

Nominal GDP is measured at current prices. If prices rise, nominal GDP rises even if output does not change. Real GDP is adjusted for inflation: it measures output at constant prices, so it shows changes in the actual quantity of goods and services produced. Economic growth is defined as an increase in real GDP.

Real GDP is calculated using a price deflator, an index of the price level with a base year value of 100:

Real GDP = nominal GDP ÷ price deflator × 100

WORKED EXAMPLE 2 Real GDP

Nominal GDP is $520 bn in 2021 and the GDP deflator is 104.7 (2020 = 100). Calculate real GDP in 2020 prices. If real GDP in 2020 was $480 bn, calculate the real growth rate.

Solution

Real GDP = 520 ÷ 104.7 × 100M1

= $496.7 bnA1

Growth = (496.7 − 480) ÷ 480 × 100 = 3.5%M1 A1

3.2 GDP per capita and PPP

A country with a large population will have a large GDP even if its people are poor. GDP per capita = GDP ÷ population gives average output per person, a better guide to living standards.

To compare countries, GDP must be converted into a common currency. Using market exchange rates can be misleading, because prices differ: $1 buys much more in India than in Switzerland. Purchasing power parity (PPP) exchange rates adjust for differences in the cost of living, so that GDP per capita at PPP compares the actual quantity of goods and services people can buy.

WORKED EXAMPLE 3 GDP per capita

Country A has GDP $2 000 bn and population 50 million; Country B has GDP $1 500 bn and population 25 million. Calculate GDP per capita for each.

Solution

A: 2 000 bn ÷ 50 m = $40 000A1

B: 1 500 bn ÷ 25 m = $60 000A1

B has a smaller GDP but higher average output per personR1

Key point

Use real GDP for growth over time, per capita for living standards, and PPP for comparisons between countries.

Quick check

1. Distinguish nominal and real GDP.

2. Why is GDP per capita better for comparing living standards?

3. What does PPP adjust for?

Answers: 1. nominal: current prices; real: adjusted for inflation 2. it allows for population size 3. differences in the cost of living between countries

4 Limitations of GDP as a measure of well-being

GDP measures output, not happiness, health or fairness.

Think about it

If a city has more car accidents, hospitals and repair shops earn more and GDP rises. Is the city better off?

GDP was designed to measure output, not well-being, and it has important limitations.

Non-market and informal activity is excluded. Unpaid work at home, such as childcare and cooking, and volunteering add to welfare but not to GDP. The informal economy, cash transactions not recorded for tax, can be very large in developing countries, so GDP underestimates their output.

Distribution is ignored. GDP per capita is an average. If all the growth goes to the richest 10%, GDP per capita can rise while most people are no better off.

Environmental damage is ignored or counted as a gain. Pollution, deforestation and depletion of natural resources reduce well-being and future output, but GDP does not subtract them. Spending to clean up pollution is even counted as an addition to GDP.

Quality of life factors are missing. Leisure time, health, education, safety, political freedom and community are not measured. A country where people work much longer hours to produce more GDP is not necessarily better off.

Quality of goods and composition of output. GDP does not capture improvements in quality (today's phones are far better than those of ten years ago at similar prices) and treats spending on weapons the same as spending on schools.

In the real world

Bhutan has famously promoted 'Gross National Happiness' as a goal alongside GDP, measuring psychological well-being, health, education, culture, environment and good governance.

Quick check

1. Give three limitations of GDP.

2. Why does GDP underestimate output in many developing countries?

Answers: 1. non-market activity, distribution, environment, quality of life 2. large informal economy

5 Alternative measures of well-being

Several indices try to measure what GDP misses.

Measure	What it includes	Strengths / weaknesses
OECD Better Life Index	11 dimensions: housing, income, jobs, community, education, environment, civic engagement, health, life satisfaction, safety, work-life balance	broad; users can weight dimensions; limited to OECD countries
Happy Planet Index	well-being and life expectancy relative to ecological footprint	links well-being to sustainability; relies on survey data
World Happiness Report	survey of life evaluations	measures subjective well-being directly; subjective and culturally influenced
Human Development Index (Unit 4)	health, education, GNI per capita	simple and widely available; ignores inequality and environment
Green GDP	GDP adjusted for environmental damage	captures sustainability; hard to value environmental losses

No single measure is perfect. Composite indicators capture more dimensions but involve choices about what to include and how to weight it. In practice, economists use GDP alongside other indicators.

6 The business cycle and output gaps

Economies grow over time, but not smoothly.

Think about it

Why might an economy grow by 5% one year and shrink by 2% the next, even though its workers and factories haven't changed much?

Figure 2. The business cycle: actual output fluctuates around the long-term growth trend (potential output).

The business cycle describes the short-term fluctuations of real GDP around its long-term trend. The trend line shows the growth of potential output: what the economy can produce when its resources are fully employed. Its upward slope reflects long-term growth in the quantity and quality of resources.

The cycle has four phases. In an expansion (recovery), real GDP rises, unemployment falls and confidence grows. At the peak (boom), output is at its highest, often above potential, and inflationary pressure builds. In a contraction, real GDP falls; if it falls for two consecutive quarters, the economy is usually said to be in recession. At the trough, output is at its lowest, unemployment is high and inflation is low.

An output gap is the difference between actual and potential output. When actual output is below potential, there is a negative (deflationary) output gap: resources, especially labour, are unemployed. When actual output is above potential, there is a positive (inflationary) output gap: resources are overused, and inflation tends to rise.

Phase	Real GDP	Unemployment	Inflation
Expansion	rising	falling	rising gradually
Peak	highest	low	high
Contraction / recession	falling	rising	falling
Trough	lowest	high	low

Common mistake

Confusing the business cycle with the long-term trend. Recessions are short-term falls below the trend; long-term growth is the upward slope of the trend itself.

Quick check

1. Define a recession.

2. What is a negative output gap?

3. What does the trend line represent?

Answers: 1. two consecutive quarters of falling real GDP 2. actual output below potential 3. potential output growth

7 Three methods of measuring national income

Output, income, expenditure.

National income can be measured by the output method (value added by all producers), the income method (wages, rent, interest, profits) and the expenditure method (C + I + G + (X − M)). In principle all three give the same total.

Figure 3. The circular flow shows why output, income and expenditure are equal.

WORKED EXAMPLE 4 Expenditure method (standard)

C = $500 bn, I = $120 bn, G = $180 bn, X = $90 bn, M = $110 bn. Calculate GDP.

Solution

500 + 120 + 180 + (90 − 110)M1

= $780 bnA1

Quick check

1. Why must the three methods give the same answer in theory?

Answers: 1. spending by one group is income to another and equals the value of output

8 Avoiding double counting

Value added.

Counting the value of intermediate goods and final goods would count the same production twice. The output method sums value added at each stage, or counts only final goods.

Stage	Sale value	Value added
farmer (wheat)	$100	$100
miller (flour)	$180	$80
baker (bread)	$300	$120
total		$300

WORKED EXAMPLE 5 Value added (standard)

Explain why GDP includes $300, not $580, for this chain.

Solution

Only final output (or sum of value added) countedR1

$580 would double count wheat and flourR1

9 GDP and GNI

Domestic versus national.

GDP measures output produced within a country's borders. GNI = GDP + net factor income from abroad (income earned by residents abroad minus income earned by foreigners domestically). For countries with large foreign investment, GNI can be much lower than GDP.

WORKED EXAMPLE 6 GNI (standard)

GDP = $400 bn; residents earn $25 bn abroad; foreigners earn $60 bn in the country. Calculate GNI.

Solution

400 + 25 − 60M1

= $365 bnA1

In the real world

Ireland's GDP is much higher than its GNI because multinational firms based there send large profits abroad; Ireland created a modified measure, GNI*, to better reflect its economy.

10 Nominal and real GDP

Adjusting for inflation.

Nominal GDP is measured at current prices; real GDP adjusts for inflation using a price deflator: real GDP = nominal GDP/price index × 100. Real GDP shows changes in actual output.

WORKED EXAMPLE 7 Real GDP (standard)

Nominal GDP rises from $500 bn to $560 bn; the price index rises from 100 to 108. Calculate real GDP in year 2 and real growth.

Solution

560/108 × 100 = $518.5 bnM1 A1

Real growth = 3.7%A1

Quick check

1. Nominal GDP grows 6% while inflation is 4%. Estimate real growth.

Answers: 1. about 2%

11 GDP per capita

Average output per person.

GDP per capita = GDP/population. It allows comparisons between countries of different sizes but hides inequality.

WORKED EXAMPLE 8 Per capita (standard)

Country A: GDP $2 trillion, population 50 million. Country B: GDP $3 trillion, population 150 million. Compare GDP per capita.

Solution

A: $40 000; B: $20 000A1 A1

A has higher average output per personR1

12 Purchasing power parity (PPP)

Comparing living standards.

Exchange rates do not reflect differences in price levels. PPP adjusts GDP so that the same basket of goods costs the same in each country, giving a better comparison of living standards. GDP per capita at PPP is higher than at market exchange rates in low-income countries.

WORKED EXAMPLE 9 PPP (exam level)

Explain why India's GDP per capita is much higher at PPP than at market exchange rates.

Solution

Many goods and services are cheaper in IndiaR1

PPP adjusts for these lower price levelsR1

13 Limitations of GDP as a measure of well-being

What GDP misses.

GDP excludes non-market activity (household work, volunteering), the informal economy, leisure, quality of goods, income distribution, environmental damage and depletion of resources. It may rise with spending on 'bads' (pollution clean-up, crime).

WORKED EXAMPLE 10 Limitations (exam level)

Explain three limitations of using GDP per capita to compare well-being.

Solution

Ignores inequality of distributionR1

Excludes non-market and informal activityR1

Ignores environmental costs and quality of lifeR1

14 Alternative measures of well-being

Beyond GDP.

Measure	What it includes
Human Development Index (HDI)	GNI per capita (PPP), life expectancy, education
Happy Planet Index	well-being, life expectancy, inequality, ecological footprint
OECD Better Life Index	11 dimensions including housing, environment, work–life balance
World Happiness Report	survey-based life satisfaction
Gross National Happiness	Bhutan's holistic measure

15 The business cycle

Fluctuations in real GDP.

Real GDP fluctuates around its long-term trend: expansion (boom), peak, contraction (recession: two consecutive quarters of negative growth), trough. The long-term trend shows potential output growth.

Figure 4. Real GDP fluctuates around a rising trend; 2020 shows a sharp contraction.

WORKED EXAMPLE 11 Recession (standard)

Define a recession.

Solution

Two consecutive quarters of negative real GDP growthA1

16 Output gaps

Actual versus potential.

A negative (recessionary) output gap exists when actual output is below potential: unemployment is high. A positive (inflationary) gap exists when actual output exceeds potential temporarily: inflation pressure rises.

Quick check

1. What happens to unemployment during a negative output gap?

Answers: 1. it rises above the natural rate

17 Green GDP

Accounting for the environment.

Green GDP subtracts the costs of environmental degradation and resource depletion from GDP. It is difficult to calculate because environmental costs are hard to value, but it gives a more sustainable picture of economic progress.

Quick check

1. Why might green GDP be lower than GDP?

Answers: 1. environmental costs and resource depletion are subtracted

18 Mixed review: worked problems

Bringing the ideas together.

WORKED EXAMPLE 12 Mixed problem (exam level)

Nominal GDP is $1200 bn in year 1 and $1320 bn in year 2; the deflator is 100 and 105. Population is 60 million in both years. Calculate real GDP per capita in year 2 and real growth.

Solution

Real GDP year 2 = 1320/1.05 = $1257 bnM1 A1

Per capita = $20 952; growth = 4.8%A1 A1

19 Additional exam-style practice

Paper 1 and Paper 3.

WORKED EXAMPLE 13 Paper 1 part (b) (exam level)

Evaluate the usefulness of GDP as a measure of economic well-being. [15]

Solution

Explain GDP and its measurementR1

Limitations with examples (inequality, environment, informal sector)R1 R1

Alternatives (HDI, PPP); judgementR1 R1

20 Index numbers in macroeconomics

Comparing over time.

Index numbers compare values to a base year (= 100). Index = (value in year/value in base year) × 100. Percentage change between years = (new index − old index)/old index × 100.

WORKED EXAMPLE 14 Index (standard)

Real GDP is $800 bn in the base year and $860 bn in year 3. Calculate the index for year 3.

Solution

860/800 × 100M1

= 107.5A1

21 The informal economy

Unrecorded activity.

The informal (shadow) economy includes unregistered work and cash transactions. It is large in many developing countries, meaning official GDP underestimates actual output.

Quick check

1. Why might official GDP underestimate output in developing countries?

Answers: 1. large informal sector not recorded

22 Comparing countries using data

Interpreting tables.

When comparing countries, use GDP per capita at PPP, consider HDI, inequality (Gini), and environmental indicators together, and be aware of data quality and differences in definitions.

Quick check

1. Why should more than one indicator be used to compare living standards?

Answers: 1. each indicator captures only part of well-being

23 Common misconceptions and links

Students often think…	Actually…
nominal GDP growth is economic growth	growth is measured by real GDP
GDP includes transfer payments	only spending on goods and services counts
higher GDP always means higher well-being	distribution, environment and quality of life matter
imports are added in GDP	imports are subtracted
a recession is any fall in GDP	usually two consecutive quarters of negative real growth

How 3.1 connects to the rest of the course

Topic	Connection
1.1 Circular flow	the basis of national income accounting
3.2 AD/AS	AD uses the same components C + I + G + (X − M)
3.3 Macroeconomic objectives	growth, unemployment and inflation over the cycle
4.8 Measuring development	HDI and other indicators

24 Exam-style question with markscheme

Try this under exam conditions (about 15 minutes) before reading the markscheme.

Figure 5. Real GDP growth and inflation in an economy.

Text A. The economy contracted in 2020 when lockdowns closed many businesses, then recovered strongly in 2021. Critics say GDP growth has not been shared fairly and has come at a cost to the environment.

(a) Identify the year of recession. [1]

(b) Nominal GDP in 2021 was $520 bn and the deflator 104.7 (2020 = 100). Calculate real GDP in 2020 prices. [2]

(d) Explain two limitations of GDP referred to in Text A. [4]

Markscheme

Part	Answer	Marks
(a)	2020	A1
(b)	520 ÷ 104.7 × 100	M1
	= $496.7 bn	A1
(c)	nominal GDP rises with prices	R1
	real GDP removes the effect of inflation	R1
	shows changes in actual output	R1
(d)	distribution: average hides who gains	R1
	explanation	R1
	environmental costs not subtracted	R1
	explanation	R1

Examiner's comments. In (b), some candidates multiplied by the deflator. In (d), only limitations referred to in the text earned marks.

25 Check your understanding

Section A: multiple choice

1. GDP measures

A. the value of final goods and services produced within a country B. the income of nationals abroad C. total wealth D. government spending

2. GNI equals GDP plus

A. depreciation B. taxes C. net income from abroad D. exports

3. Real GDP is

A. GDP at current prices B. nominal GDP adjusted for inflation C. GDP per capita D. GDP in US dollars

4. Which is an injection?

A. saving B. taxes C. imports D. exports

5. PPP adjusts for

A. inflation over time B. differences in the cost of living C. population D. unemployment

6. A recession is often defined as

A. two consecutive quarters of negative real GDP growth B. high inflation C. falling unemployment D. a trade deficit

7. Which is excluded from GDP?

A. teachers' salaries B. investment in machinery C. exports D. unpaid household work

8. A positive output gap means

A. actual output is below potential B. GDP is falling C. actual output is above potential D. unemployment is high

Section B: structured

9. C = 500, I = 120, G = 180, X = 90, M = 110 ($ bn). Calculate GDP. [2]

10. Explain the difference between GDP and GNI. [3]

11. Evaluate GDP as a measure of living standards. [8]

12. Using a diagram, explain the phases of the business cycle. [4]

Answers

1. A 2. C 3. B 4. D 5. B 6. A 7. D 8. C

9. 500 + 120 + 180 + (90 − 110) = $780 bn.

10. GDP: output within the country; GNI: income of residents wherever earned; GNI = GDP + net income from abroad.

11. Strengths: widely available, correlates with health/education; limitations: distribution, environment, informal sector, quality of life; alternatives; judgement.

12. Expansion, peak, contraction, trough around the trend; output gaps.

26 Summary and topic map

Idea	Remember
Circular flow	income = output = expenditure
Equilibrium	S + T + M = I + G + X
GDP	C + I + G + (X − M)
GNI	GDP + net income from abroad
Real GDP	nominal ÷ deflator × 100
Per capita / PPP	per person / adjusted for cost of living
Limitations	informal economy, distribution, environment, quality of life
Business cycle	expansion, peak, contraction, trough; output gaps

Before the exam, make sure you…

•subtract imports in the expenditure method
•use real GDP for growth and per capita for living standards
•link each limitation to a specific example
•label the trend and output gaps on the cycle diagram

Measuring Economic Activity on one page

Cover this page with a sheet of paper and try to rebuild it from memory. Whatever you can't recall is what to revise next.

Figure 6. Topic map for Measuring Economic Activity.

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