Macroeconomics (SL) — IB Economics SL SL Study Guide

For: IB Economics SL candidates sitting IB Economics SL.

Covers: All core SL Macroeconomics syllabus content including GDP and economic activity measurement, AD-AS model fundamentals, inflation and unemployment dynamics, and introductory fiscal and monetary policy tools.

You should already know: Basic literacy in current affairs and arithmetic.

A note on the practice questions: All worked questions in the "Practice Questions" section below are original problems written by us in the IB Economics SL style for educational use. They are not reproductions of past IBO papers and may differ in wording, numerical values, or context. Use them to practise the technique; cross-check with official IBO mark schemes for grading conventions.

1. What Is Macroeconomics (SL)?

Macroeconomics is the study of the economy as a whole, focusing on aggregate indicators, systemic trends, and government policy impacts on national economic performance, rather than individual household or firm choices (the domain of microeconomics). For IB SL, this topic is weighted at 30% of your final exam score, with questions appearing in both Paper 1 (essay) and Paper 2 (data response). Common synonyms include aggregate economics and national economic analysis, and it forms the foundation for all higher-level macro content and cross-topic evaluation questions.

2. GDP and economic activity

Gross Domestic Product (GDP) is the most widely used measure of national economic activity, defined as the total market value of all final goods and services produced within a country’s geographic borders over a specific time period (usually 1 calendar year). Four non-negotiable criteria apply to GDP calculations for IB exams: you must exclude intermediate goods (to avoid double-counting), exclude resale of used goods produced in prior periods, only count activity within the country’s borders, and only count activity sold in formal markets (exclude unpaid household work and unreported informal sector activity).

The expenditure method of calculating GDP is the most frequently tested in SL exams, and follows this formula: $$GDP=C+I+G+(X-M)$$ Where:

• $C$ = household consumption spending on goods and services
• $I$ = firm investment spending on capital goods, new housing, and inventory changes
• $G$ = government spending on public goods and services (exclude welfare transfer payments, as these are not payments for produced output)
• $X$ = export revenue from goods and services sold to other countries
• $M$ = import spending on goods and services purchased from other countries

Worked example

Country X reports 2025 economic data as follows: C = $310bn,I=$75bn, G = $110bn(including$25bn in welfare payments), X = $65bn,M=$45bn. Calculate 2025 GDP for Country X:

1. First, remove the $25bnwelfaretransferfromG:adjustedG=$110bn - $25bn=$85bn
2. Plug values into the formula: $310+$75 + $85+($65 - $45)=$310 + $75+$85 + $20=$490bn

You should also distinguish nominal GDP (calculated using current year prices) and real GDP (adjusted for inflation using a fixed base year price level) for exam questions: real GDP is the only valid measure of changes in actual output volume over time.

3. AD-AS model basics

The Aggregate Demand-Aggregate Supply (AD-AS) model is the core analytical framework for SL macroeconomics, used to explain changes in output, unemployment, and price levels in an economy.

• Aggregate Demand (AD): The total planned spending on all goods and services in an economy at every possible price level in a given period. The AD curve slopes downward because of three effects: the wealth effect (higher prices reduce the purchasing power of household savings, lowering consumption), the interest rate effect (higher prices raise demand for money, pushing up interest rates and reducing firm investment), and the international trade effect (higher domestic prices make exports less competitive, reducing net exports). Only non-price changes to C, I, G, or (X-M) shift the AD curve; changes in the price level only cause movements along the existing AD curve.
• Aggregate Supply (AS): The total quantity of goods and services firms are willing and able to produce at every possible price level. For SL, you only need to know two AS curves:

1. Short-Run AS (SRAS): Upward sloping, because input prices (wages, raw materials) are sticky (fixed by contracts) in the short run, so higher output prices raise firm profit margins and encourage higher production. Changes in input prices or supply shocks shift the SRAS curve.
2. Long-Run AS (LRAS): Vertical at the full employment level of output ($Y_f$), the output level where cyclical unemployment is zero. In the long run, all input prices adjust to price level changes, so changes in the price level do not affect total output.

Macroeconomic equilibrium occurs where AD intersects SRAS. If this intersection is exactly at $Y_f$, the economy is at long-run equilibrium; if it is left of $Y_f$, there is a recessionary gap (unused capacity, cyclical unemployment); if it is right of $Y_f$, there is an inflationary gap (overheating, upward pressure on prices).

4. Inflation, unemployment

Inflation and unemployment are the two core indicators of macroeconomic health tested in SL exams.

• Inflation: A sustained increase in the general (average) price level across the whole economy over time, measured by the Consumer Price Index (CPI), which tracks the price of a weighted basket of commonly purchased consumer goods and services. Disinflation is a slowdown in the rate of inflation, while deflation is a sustained fall in the general price level. The two most common causes of inflation are demand-pull inflation (AD rises faster than AS, creating an inflationary gap) and cost-push inflation (SRAS shifts left due to rising input costs like oil or wages).
• Unemployment: The number of people of working age who are willing and able to work, actively seeking work, but cannot find paid employment. The unemployment rate is calculated as: $$\text{Unemployment Rate}=\frac{\text{Number of Unemployed}}{\text{Total Labor Force}}\times 100$$ The labor force only includes people of working age who are either employed or actively seeking work, excluding students, retirees, and people not looking for paid work. For SL, the three key types of unemployment are frictional (temporary unemployment between jobs), structural (long-term unemployment from a mismatch between worker skills and available jobs, e.g., from factory closures), and cyclical (unemployment caused by a recessionary gap, when AD is too low to support full employment).

Examiners frequently ask you to explain the short-run negative relationship between inflation and cyclical unemployment (the short-run Phillips curve) in essay questions: as AD rises, cyclical unemployment falls but inflation rises, and vice versa.

Worked example

A country has a labor force of 22 million people, of which 1.32 million are unemployed. 0.3 million are frictional, 0.2 million are structural, and the remainder are cyclical. Calculate the total unemployment rate and the size of the recessionary gap:

1. Unemployment rate = ($1.32 / 22) * 100 = 6%
2. Cyclical unemployment = 1.32 - 0.3 - 0.2 = 0.82 million, so the economy has a clear recessionary gap requiring demand-side policy intervention.

5. Fiscal and monetary policy intro

Fiscal and monetary policy are the two core demand-side policy tools used by governments and central banks to close output gaps, tested extensively in both Paper 1 and Paper 2.

• Fiscal policy: Controlled by the national government, using changes in government spending (G) and taxation (T) to shift the AD curve. Expansionary fiscal policy (rise in G, cut in direct or indirect taxes) shifts AD right to close recessionary gaps, reducing cyclical unemployment but risking higher inflation and increased government debt. Contractionary fiscal policy (cut in G, rise in taxes) shifts AD left to close inflationary gaps, reducing inflation but risking higher cyclical unemployment. The impact of government spending is amplified by the spending multiplier, calculated as: $$k=\frac{1}{1-MPC}$$ Where MPC is the marginal propensity to consume, the share of additional household income spent on domestic goods and services.
• Monetary policy: Controlled by the independent central bank, using changes in interest rates, money supply, and exchange rates to shift the AD curve. Expansionary monetary policy (cut in base interest rates, increase in money supply) lowers borrowing costs for households and firms, raising C and I, and usually lowers the exchange rate to boost exports, shifting AD right to close recessionary gaps. Contractionary monetary policy (rise in base interest rates, reduction in money supply) shifts AD left to reduce high inflation.

Worked example

An economy has a $30bn recessionary gap, and the MPC is 0.8. Calculate the required increase in government spending to close the gap:

1. Calculate the multiplier: $k=1/(1-0.8)=5$
2. Required G increase = $30bn/5=$6bn: a $6bnriseinGwillshiftADrightby$30bn, closing the recessionary gap.

6. Common Pitfalls (and how to avoid them)

• Wrong move: Counting intermediate goods or transfer payments when calculating GDP, e.g., adding the value of steel used to make a car plus the final value of the car, or including welfare payments in G. Why: Students forget the "final goods only" rule and that transfer payments are not payments for produced output. Correct move: Only include the value of finished goods and services, and subtract transfer payments from government spending values provided in exam questions.
• Wrong move: Confusing a shift of the AD/AS curve with a movement along the curve, e.g., stating a rise in the price level reduces AD. Why: Students mix up price level changes (which only cause movements along existing curves) and non-price determinants (which shift curves). Correct move: Explicitly state that only changes to C, I, G, X-M shift AD, and only changes to input prices or productivity shift AS.
• Wrong move: Defining deflation as a fall in the price of a single good or a one-off fall in the general price level. Why: Students ignore the "sustained" and "general" requirements for inflation/deflation definitions, which are explicitly tested in 2-mark definition questions. Correct move: Always reference that inflation/deflation is a sustained change in the average price level across the whole economy.
• **Wrong move: Calculating unemployment rate using total population instead of the labor force. Why: Students forget the labor force excludes people not actively seeking work. Correct move: Always confirm the denominator is the total of employed + unemployed people, not the entire working age or total population.
• Wrong move: Only listing benefits of policy interventions without mentioning trade-offs in essay questions. Why: Examiners award marks for evaluation, not just memorization of policy effects. Correct move: Always note trade-offs: expansionary policy risks higher inflation and debt, contractionary policy risks higher unemployment, and supply-side policies take longer to take effect.

7. Practice Questions (IB Economics SL Style)

Question 1 (Paper 2 Data Response, 2 marks)

Country Y reports 2025 economic data: Household consumption = $280bn,Firminvestment=$82bn, Government spending (including $30bninpensiontransfers)=$130bn, Export revenue = $72bn,Importspending=$54bn. Calculate Country Y’s 2025 GDP using the expenditure method.

Solution

1. First, remove transfer payments from government spending: Adjusted G = $130bn-$30bn = $100bn
2. Apply the GDP formula: $280+$82 + $100+($72 - $54)=$280 + $82+$100 + $18=$480bn Full marks awarded for excluding transfers and correct final calculation.

Question 2 (Paper 1 Essay Part a, 4 marks)

Using the AD-AS model, explain the difference between cost-push and demand-pull inflation.

Solution

• Demand-pull inflation occurs when AD rises faster than AS, shifting the AD curve right, creating an inflationary gap above $Y_f$: excess demand pushes up prices as firms operate beyond full capacity. It is usually caused by higher consumer confidence, lower taxes, or rising export demand.
• Cost-push inflation occurs when SRAS shifts left due to rising input costs (e.g., higher global oil prices, minimum wage rises), reducing equilibrium output and raising the price level at the same time, leading to stagflation (high inflation + high unemployment). 2 marks awarded per inflation type explanation, with 1 additional implicit mark for correct AD-AS model referencing.

Question 3 (Paper 2 Calculation, 4 marks)

A country has a working age population of 40 million: 3 million are full-time students not seeking work, 4 million are retired, 2 million are stay-at-home parents not seeking work, 29.1 million are employed, and 0.9 million are actively seeking paid work. (a) Calculate the size of the labor force (2 marks), (b) Calculate the unemployment rate (2 marks).

Solution

(a) Labor force = employed + unemployed = 29.1 million + 0.9 million = 30 million. Alternative calculation: 40 million - 3m - 4m - 2m = 30 million. Full marks for correct answer. (b) Unemployment rate = (0.9 / 30) * 100 = 3%. Full marks for correct calculation.

8. Quick Reference Cheatsheet

9. What's Next

This core Macroeconomics SL content is the foundation for all remaining macro topics in the IB syllabus, including economic growth, sustainable development, and international trade. You will use the AD-AS model repeatedly to analyse the impact of external shocks (such as global oil price rises or pandemics) on national economies, and to evaluate the effectiveness of government policy responses in both essay and data response questions. A strong grasp of these core concepts will also make it easier to connect macroeconomic outcomes to microeconomic behaviour, a common cross-topic exam question theme that is weighted heavily for higher mark bands.

To reinforce your understanding, practise applying these concepts to real-world current affairs, such as recent interest rate changes by central banks or government spending announcements, to test your ability to analyse policy impacts as required by the IBO mark schemes. If you get stuck on any calculation, model application, or exam question structure, you can ask Ollie for personalized explanations, worked examples, and extra practice questions at any time on the homepage.