Key Idea: Is the country better off this year than last year? To answer that you need one number for everything it made: every phone, haircut, bus ride and school lesson. That number is GDP. The rest of the topic is about reading it honestly: take out price rises (real), share it out per person (per capita), make it comparable across countries (PPP), and then notice what the number still misses. Plotted over time, GDP rises in waves: the business cycle. Where you meet it:
Paper 1
- Essays.
- Discuss [15]: how useful real GDP per capita, or GNI, is as a measure of well-being.
Paper 2
- Data response.
- Calculate [1 to 3]: GDP from its parts, GNI, real GDP from a deflator, GDP per capita, a growth rate.
- Define [2]: GDP, the informal economy, recession.
- Sketch [2 or 3]: a business cycle with a recession or an output gap marked.
Every later unit
- The same letters, a new name.
- C + I + G + (X − M) becomes aggregate demand in 3.2.
- Every policy question in Unit 3 starts from where the economy sits on the business cycle.
📊 GDP: one number, three ways to count it
Gross domestic product is the total value of all final goods and services produced inside a country in a year. You can count it three ways and get the same total: add up what firms produce (output), add up what people earn from producing it (income), or add up what is spent on it (spending). The spending route is the one you use.
- consumption: what households spend
- investment: what firms spend on capital, such as machines and buildings
- government spending on goods and services
- exports: what foreigners spend on this country's output
- imports: what this country spends on foreign output (subtracted)
Final means the tyres on a new car are counted once, inside the car's price. Count the tyres and the car and the total is wrong. Inside means location, not ownership: a Japanese-owned factory in Mexico adds to Mexico's GDP. Imports are subtracted. They were bought here but made abroad, so they are not this country's output.
🌐 GDP or GNI: made here, or earned by us
GDP asks where the output was made. Gross national income asks who earned the income. A country whose people and firms earn a lot abroad has GNI above GDP. A country full of foreign-owned factories sending profits home has GNI below GDP.
- gross national income: what the country's residents earn, wherever they earn it
- gross domestic product: what is produced inside the country's borders
- income residents earn abroad minus income foreigners earn inside the country; it can be negative
Important: A data table often gives the two flows separately. Subtract to get net income from abroad first, keep its sign, then add it to GDP. If the question gives GDP and GNI and asks for net income from abroad, it is simply GNI − GDP.
💰 Real, per capita, PPP: making the number honest
Nominal GDP is measured at this year's prices, so it rises when prices rise even if nothing more is made. Real GDP is measured at the prices of a base year, so it only rises when output rises. Real GDP is the one that tells you whether the country actually produced more.
- GDP at the prices of the base year, so only output changes move it
- GDP at this year's prices
- a price index that equals 100 in the base year; 120 means prices are 20% higher than then
Real: take out inflation with the deflator. Per capita: divide by the population, because a bigger country sharing the same total has less each. PPP: convert at what the money actually buys, because $1 buys more in India than in Norway. Real GDP per capita at PPP is the figure for comparing living standards between countries. Nominal total GDP compares the size of economies, nothing more.
⚠️ What GDP leaves out
GDP counts output that is sold. Well-being includes a lot that is not sold, and some things GDP counts make life worse. Each gap below is an evaluation point in a 15-mark essay.
| What GDP misses | Why the figure misleads | Example |
|---|---|---|
| Who gets it | per capita is an average; it says nothing about distribution | a country where a few families own the oil and most people are poor |
| Unpaid work | childcare, cooking and volunteering at home are output but never sold | a parent who leaves work to raise children lowers GDP and raises well-being |
| The informal economy | undeclared, untaxed activity is not recorded, so GDP is understated | cash-in-hand building work, street markets, unregistered taxis |
| Damage | pollution is not subtracted, and cleaning it up is added | a chemical spill raises GDP twice: the factory's output and the clean-up |
| Quality of life | health, leisure, safety and freedom have no price | two countries with the same GDP per capita but very different life expectancy |
| Sustainability | selling off forests and oil counts as income, not as using up capital | a country that logs its forests grows fast this year and has nothing left in ten |
The informal economy: economic activity that is not recorded, regulated or taxed by the government, such as undeclared cash-in-hand work. Big in many developing countries, so their official GDP understates real output. When an essay asks what to use instead, name an alternative indicator: the Human Development Index adds life expectancy and years of schooling to income per person.
📈 The business cycle and output gaps
Real GDP rises over time, but in waves around a rising trend line, which shows potential output. The wave goes expansion → peak → contraction → trough, then round again. A recession is two consecutive quarters of falling real GDP. Shocks to spending (confidence, exports) or to costs (oil prices, a pandemic) push the economy off the trend.
Where actual real GDP sits above potential output there is a positive (inflationary) output gap: the economy is producing more than it can sustain and prices are pushed up. Where it sits below there is a negative (recessionary) output gap: spare capacity, unemployment above normal. The trend line slopes upward. Drawn flat, your diagram says the economy never grows.
🔢 Doing the sums
Every calculation in this topic is built from the same four moves, and every step should be visible on the page: formula, substitution, answer with its unit.
From the data table to the answer
- Write the formula — GDP = C + I + G + (X − M), or GNI = GDP + net income from abroad. Write it down first, so the method shows even if a later number slips.
- Substitute, minus the imports — Put every figure in, in the currency and units the table uses. Imports are subtracted; adding them is the most common slip in the whole topic.
- Deflate, then divide — Real = nominal ÷ deflator × 100. Only then divide by the population for per capita. Billions ÷ millions gives thousands per person, so check the size of your answer makes sense.
- Growth rate and the unit — Growth rate = (new − old) ÷ old × 100, in %. Use real GDP, not nominal. Round as asked, and end with the unit: billions of dollars, dollars per person, or %.
Formula → substitute → deflate → divide by people → unit
Important: Adding imports. Forgetting the ×100 when deflating, which makes real GDP a hundred times too small. Reporting a growth rate from nominal figures, which mixes price rises in with real growth.
✍️ Worked examples
The four shapes this topic is asked in, with new scenarios. Try each before opening the plan.
A country's national accounts show, in billions of dollars: consumption 560, investment 140, government spending 210, exports 180, imports 220. Its residents earned 45 abroad, and foreign residents earned 75 inside the country. Calculate the country's gross national income.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
Now the deflating question.
In 2025 a country's nominal GDP was 1 260 billion dollars, its GDP deflator was 120 (base year 2020 = 100) and its population was 21 million. Calculate real GDP per capita in 2025.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
Now the sketch.
A text reports that a country's real GDP has fallen for three quarters in a row while its potential output has kept growing. Sketch a business cycle diagram showing actual real GDP falling below potential output.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
And the Paper 1 shape.
Using real-world examples, discuss the view that gross national income is a useful measure of a country's well-being.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
✅ Quick self-check
Tap each card to check yourself.
Define gross domestic product. The total value of all final goods and services produced within a country's borders in a given period, usually a year.
GDP is 900 billion and GNI is 860 billion. What is net income from abroad? GNI − GDP = 860 − 900 = −40 billion. Foreigners earned more inside the country than its residents earned abroad.
Nominal GDP is 880 billion and real GDP is 800 billion. Calculate the deflator. Deflator = nominal ÷ real × 100 = 880 ÷ 800 × 100 = 110. Prices are 10% higher than in the base year.
Real GDP rises from 1 050 billion to 1 092 billion. What is the growth rate? (1 092 − 1 050) ÷ 1 050 × 100 = 42 ÷ 1 050 × 100 = 4%.
Why compare countries at PPP rather than at market exchange rates? Because the same dollar buys different amounts in different countries. PPP converts at what money actually buys, so the comparison reflects what people can afford.
Define the informal economy. Economic activity that is not recorded, regulated or taxed by the government, such as undeclared cash-in-hand work. It is missing from official GDP.
Define recession. A fall in real GDP over two consecutive quarters. Slower growth is not a recession; output has to fall.
Actual real GDP is above the trend line. What kind of output gap, and what does it do to prices? A positive (inflationary) output gap. The economy is producing more than it can sustain, so prices are pushed up.
Exam tips
- Formula, substitution, answer with the unit: three visible steps for every Calculate, even a 1-mark one.
- Imports are subtracted. Say it to yourself before every GDP calculation.
- GDP is location, GNI is ownership. Net income from abroad can be negative; keep the sign.
- Deflate first, then divide by the population. Real = nominal ÷ deflator × 100.
- For a growth rate use real GDP and divide by the old value. Nominal growth mixes in price rises.
- Define and then add one more element: GDP with the word final and within the borders; recession with two consecutive quarters.
- Business cycle sketch: real GDP up the side, time along the bottom, an upward trend line labelled potential output, and only the labels the question asks for.