IB Economics Paper 3 November 2025

IB Economics HL Paper 3 November 2025 - Full Exam Breakdown

Exam: IB Economics Paper 3 | Higher Level only | November 2025
Duration: 1 hour 45 minutes | Total marks: 60 | Calculator permitted
Instruction: Answer ALL questions

This page gives you a teacher-led, mark-scheme-informed breakdown of every question on the IB Economics HL Paper 3 November 2025. Question 1 was built around the United States economy - covering real GDP growth rate calculation, real interest rates, money creation, quantitative easing, the money market diagram, current account and financial account calculations, exchange rate percentage change, and the AD/AS link between dollar depreciation and demand-pull inflation, finishing with a 10-mark policy recommendation on correcting the persistent current account deficit.

Question 2 used Indonesia's development challenges as the context for comparative advantage, production possibility curves, the limits of specialisation theory, negative production externalities in the palm oil market, profit and marginal cost calculations, identifying the socially optimal output level, constructing a Lorenz curve, causes of income inequality, calculating welfare loss from a subsidy diagram, and a 10-mark recommendation on reducing carbon emissions.

All calculations have been fully worked. Diagram requirements are explained in detail. Both 10-mark extended responses are broken down by mark band.

Paper 3 Format - The Key Facts

Paper 3 is HL-exclusive and carries 60 marks over 1 hour 45 minutes. Every question is compulsory - no choices. The paper consistently mixes numerical work and calculations, short diagram questions, conceptual definitions, and a 10-mark "recommend" essay in each question. The November 2025 session was particularly demanding in terms of content:

Question 1 alone covered seven distinct calculation or diagram sub-questions before reaching the essay, drawing on monetary policy theory, balance of payments accounting, and exchange rate analysis.

Question 2 introduced comparative advantage and production possibility curves - topics less common in recent Paper 3 sittings - alongside a detailed palm oil externalities question with a data table requiring multiple separate calculations, and the identification of the socially optimal output.

The 10-mark "recommend" command word requires: identification of a policy, use of economic theory to support it, appropriate terminology, integration of text and data from the question, and balanced evaluation. A response that discusses theory without relating it to the specific numbers and context the question offers will not reach Band 4 or 5.

Question 1 - The USA Economy: Macroeconomics, Monetary Policy, and the Balance of Payments

The context for Question 1 was the US economy from 2020 to 2023. The stimulus/reference material established three key facts about the USA: it is the world's largest economy, it has the world's largest budget deficit, and it has the world's largest current account deficit. Table 1 gave real GDP figures from 2020 to 2023 with one missing growth rate. The Federal Reserve's 2% inflation target was mentioned, with actual inflation of 3.1% (January 2023 to January 2024) and a nominal borrowing rate of 8.5%. Table 2 provided quarterly balance of payments data for 2023. Figure 1 showed the USD/CNY exchange rate from September to December 2023.

Question 1(a)(i) - Calculate GDP Growth Rate for 2023 [1 mark]

Command term: Calculate - work out a numerical answer.

Formula: GDP growth rate = ((GDP current year − GDP previous year) ÷ GDP previous year) × 100

Worked answer:

Growth rate (2023) = ((22,668 − 21,989) ÷ 21,989) × 100 = (679 ÷ 21,989) × 100 = 3.09%

Mark scheme: 3.09% or 3.09 without working earns [1]. Correct rounding beyond 2 decimal places is also accepted (e.g., 3.088). The answer should be entered in Table 1.

Lawrence's note: The 2022 growth rate of 0.65% reflects the sharp slowdown after the post-pandemic rebound of 5.42% in 2021. The 3.09% growth in 2023 - well above the prior year and above the Fed's inflation target of 2% - this is one of the reasons why the Federal Reserve maintained high interest rates throughout 2023. This sets up the real interest rate calculation in (ii) and the balance of payments questions that follow.

Common errors: Using 2020 as the base year rather than 2022. Calculating the change in GDP without expressing it as a percentage of the previous year. Rounding to one decimal place (3.1%) - technically acceptable but less precise than the required two decimal places.

Question 1(a)(ii) - Calculate the Real Interest Rate [1 mark]

Command term: Calculate - apply the Fisher equation.

Formula: Real interest rate = Nominal interest rate − Inflation rate

Worked answer:

Real interest rate = 8.5% − 3.1% = 5.4%

Mark scheme: 5.4% or 5.4 without working earns [1].

Lawrence's note: A positive real interest rate of 5.4% means that borrowers in the USA were paying significantly more in real terms to borrow money - their debt is growing faster than inflation is eroding it. This is a contractionary environment, which is exactly what the Federal Reserve intended: by keeping nominal rates at 8.5% against a 3.1% inflation rate, the Fed was actively discouraging borrowing and spending in order to bring inflation back towards its 2% target. Compare this to the Japan question in May 2025, where the real interest rate was −0.2% - this was the opposite monetary challenge.

Common errors: Subtracting the nominal rate from inflation (getting −5.4%). Using the GDP growth rate (3.09%) instead of the inflation rate (3.1%) - a careless error when reading the data.

Question 1(a)(iii) - Explain How Commercial Banks Create Money [4 marks]

Command term: Explain - give a clear account showing how the process works.

Mark scheme structure: This question is assessed by bullet-point achievement rather than levels. Each bullet point earns [1], up to [4]. Four marks require either four bullet points or three bullet points plus a correct quantitative example.

The four mark-scheme bullet points:

[1] An increase in commercial bank reserves - through a customer cash deposit or through the central bank's open market purchases of bonds - increases the bank's available funds.

[1] This allows the bank to lend out a portion of these additional reserves to customers.

[1] The quantity of possible loans depends on the minimum reserve requirement (MRR) or required reserve ratio (RRR). The bank must keep a fraction in reserve and can lend the rest.

[1] These loans create new money - when borrowers spend the loans, the funds are deposited in other banks, which then lend a further fraction, and the process repeats itself across the banking system.

The quantitative example route to [4]: If the reserve requirement is, say, 10%, then a $1,000 deposit allows $900 to be lent. That $900 is deposited elsewhere, allowing $810 to be lent, and so on. The money multiplier = 1 ÷ reserve requirement = 1 ÷ 0.10 = 10, so in theory the maximum possible expansion is $1,000 × 10 = $10,000.

Common errors: Describing QE rather than commercial bank money creation - these are different processes. Stating that banks lend out all deposits without mentioning the reserve requirement. Stopping after one round rather than explaining the iterative, repetitive, multiplier process. Confusing money creation with money printing (only central banks print notes; commercial banks create money through lending).

Lawrence's notes: Notice that this question appeared in both the May 2025 Paper 3 (as an "explain the process with a specific JPY 10,000 deposit and 0.8% reserve requirement") and here in November 2025 (as a general "explain how commercial banks create money" without specific numbers). The May version required more precision because specific figures were given. The November version rewards the same conceptual understanding but gives more flexibility - a correct qualitative explanation of all four stages earns full marks even without numbers.

Question 1(a)(iv) - Outline What Is Meant by Quantitative Easing [2 marks]

Command term: Outline - give a brief account.

Mark scheme levels:

Level 1 [1 mark]: Quantitative easing is a form of expansionary monetary policy, OR the central bank purchases financial assets from commercial banks - but the candidate does not include both.

Level 2 [2 marks]: Quantitative easing is a form of expansionary monetary policy AND the central bank purchases financial assets from commercial banks.

Lawrence's notes:

Quantitative easing (QE) is used when conventional monetary policy - cutting interest rates - has already been implemented and further rate cuts are not possible (the "zero lower bound" problem). The central bank creates new digital reserves and uses them to purchase financial assets (primarily government bonds, but also corporate bonds and mortgage-backed securities) from commercial banks. This increases commercial bank reserves, reduces long-term interest rates, lowers bond yields, and is designed to stimulate borrowing, investment, and spending.

The Fed conducted four rounds of QE between 2008 and 2023, totalling USD 8,900 billion - an extraordinary scale of intervention. In theory, this increases the money supply (consistent with part (iii)), reduces long-term interest rates (consistent with part (v)), and stimulates aggregate demand.

Common errors: Describing QE as "the government printing money" - technically the central bank creates digital reserves, which is not the same as printing banknotes. Defining QE without mentioning financial asset purchases. Confusing QE with open market operations - QE is a type of open market operation, but it targets specifically longer-maturity assets and is used when conventional interest rate cuts are no longer effective.

Question 1(a)(v) - Sketch the Money Market Diagram [2 marks]

Command term: Sketch - draw a clearly labelled diagram.

What the question asked: Sketch a diagram to show how an increase in the money supply is expected to affect the equilibrium interest rate.

Diagram requirements:

• Y-axis: Interest rate (or real interest rate, nominal interest rate, discount rate, cost of borrowing - all acceptable)

• X-axis: Quantity of money (or just "Quantity")

• A downward-sloping money demand curve labelled MD (or DM or D)

• Two vertical money supply curves: MS1 (original) and MS2 (shifted right) - labelled MS, SM, or S

• Interest rate falls from r1 to r2, shown clearly via labels or arrows

• New equilibrium at higher quantity of money and lower interest rate

Critical requirement: The money supply curves must be vertical. This is the key distinguishing feature of the money market model. The central bank controls the money supply directly; it does not slope upward like a typical supply curve. Any money supply curve drawn with a positive slope cannot earn full marks.

Mark scheme levels:

Level 1 [1 mark]: A correct diagram showing an increase in money supply and a fall in the interest rate, but with incorrect labelling or omissions (e.g., missing axis labels, or no IR1/IR2 labels showing the change).

Level 2 [2 marks]: A fully correct diagram with vertical money supply curves, a shift from MS1 to MS2, a clear fall in interest rate from r1 to r2, and labelled axes.

Common errors: Drawing the money supply as an upward-sloping curve (the most common error by far - students confuse the money market with a goods market). Shifting the money demand curve rather than the money supply. Showing interest rates rising when money supply increases (getting the direction wrong). Forgetting to show the original equilibrium (r1, Q1) before the shift.

Lawrence's notes: The economic process / understanding is is as follows: the central bank increases the money supply (MS shifts right). At the existing interest rate, there is now an excess supply of money. People and banks use this excess money to purchase bonds and other assets, driving bond prices up and interest rates down. The new equilibrium has more money in circulation at a lower interest rate. This mechanism is exactly how QE (described in (iv)) is intended to stimulate the economy - lower interest rates should encourage borrowing and investment.

Question 1(a)(vi) - Calculate Balance of Trade in Goods and Services Q3 [1 mark]

Command term: Calculate - single arithmetic operation from Table 2.

Worked answer:

Balance of trade (Q3) = Exports − Imports = 1,178 − 1,374 = −USD 196 billion (deficit)

Mark scheme: An answer of −196 or "196 billion deficit" without working earns [1].

Common errors: Using the full year figure rather than Q3 only. Subtracting in the wrong direction (getting +196 as a surplus). Forgetting to state clearly whether it is a deficit or surplus.

Lawrence's notes: The Q3 trade deficit of USD 196 billion was the largest of the four quarters shown. Across all four quarters in 2023, the USA ran consistent trade deficits - proving the text's statement that the USA has the world's largest current account deficit, driven by high labour costs, labour unions, and skills shortages in STEM as the main structural factors reducing export competitiveness.

Question 1(a)(vii) - Calculate the Financial Account for Q4 [3 marks]

Command term: Calculate - use the balance of payments identity.

The key principle: The balance of payments must add to zero. Therefore: Current account + Capital account + Financial account = 0. Rearranging: Financial account = −(Current account + Capital account).

Step 1 - Calculate the current account for Q4:

Current account = (Exports − Imports) + Net income + Net current transfers

= (1,180 − 1,375) + 36 + (−39)

= −195 + 36 − 39

= −USD 198 billion

Step 2 - Note the capital account for Q4:

Capital account = −USD 2 billion (given in Table 2)

Step 3 - Apply the BOP identity:

Financial account = −(−198 + (−2)) = −(−200) = +USD 200 billion (surplus)

Mark scheme breakdown: [1] for any valid working including current account data only. [1] for arriving at −200 (the combined current and capital account total). [1] for stating the financial account = USD 200 billion. Full marks require valid working AND correct units. OFR applies if the working is incorrect but the final answer correctly shows that all accounts sum to zero.

Lawrence's notes: Why the financial account is positive (surplus): A current account deficit must be financed. The USA's persistent current account deficit means it is spending more on foreign goods, services, and transfers than it is receiving - so foreigners are accumulating dollars. Those dollars flow back into the USA's financial account as foreign investment in US assets (US Treasury bonds, equities, property). This is the exact mirror image of the current account deficit: the USA "borrows" from the rest of the world by selling it financial assets, which shows up as a financial account surplus. This is what the text means when it implies the current account deficit reflects structural dependency on foreign capital.

Common errors: Calculating only the balance of trade (exports − imports) and ignoring net income and net current transfers. Forgetting to include the capital account. Getting the sign of the financial account wrong (stating a deficit of 200 rather than a surplus). Not understanding the BOP identity and attempting to calculate the financial account directly from data that isn't given.

Question 1(a)(viii) - Percentage Change in USD/CNY [2 marks]

Command term: Calculate - read values from Figure 1 and apply the percentage change formula.

Reading Figure 1: The y-axis shows CNY per USD. A higher value means the USD is worth more CNY - i.e., the USD is stronger. A falling value means the USD is depreciating against the CNY.

Highest point in September 2023: approximately 7.35 CNY per USD

Lowest point in December 2023: approximately 7.10 CNY per USD

Formula: Percentage change = ((New value − Original value) ÷ Original value) × 100

Worked answer:

% change = ((7.10 − 7.35) ÷ 7.35) × 100 = (−0.25 ÷ 7.35) × 100 = −3.40%

Mark scheme notes: [1] for any valid working. [1] for the correct answer of −3.4%. A slight misreading of the graph (e.g., using 7.09 or 7.095 for the December low) is acceptable and gives −3.47% or −3.54% - all awarded full marks. An unsupported answer without explanation offered of −3.4 earns [1].

Lawrence's notes: What this depreciation means: A fall from 7.35 to 7.10 means 1 USD now buys fewer CNY. From China's perspective, US goods have become cheaper to buy. From the US perspective, Chinese goods have become more expensive. This sets up the mechanism in question (ix) - a depreciating dollar should boost US exports to China and reduce US imports from China, improving the trade balance and increasing aggregate demand.

Common errors: Reading the graph in the wrong direction (identifying the highest point as the lowest). Using the December high rather than the December low. Calculating the absolute change rather than the percentage change. Getting a positive answer (which would imply the dollar appreciated).

Question 1(a)(ix) - AD/AS Diagram: Dollar Depreciation and Demand-Pull Inflation [4 marks]

Command term: Explain - use the diagram to support a causal argument.

What the question asked: Using an AD/AS diagram, explain why a depreciating dollar may lead to demand-pull inflation in the USA.

The transmission mechanism (the chain of reasoning):

Dollar depreciates → US goods become cheaper for foreign buyers (in their own currencies) → US exports increase → Foreign goods become more expensive for American buyers (in dollars) → US imports decrease → Net exports (X − M) increase → Net exports is a component of aggregate demand (AD = C + I + G + (X − M)) → AD increases → AD curve shifts rightward → Intersection with SRAS curve is at a higher price level → Demand-pull inflation.

Diagram requirements:

• Y-axis: Price level (PL)

• X-axis: Real GDP (or Real output)

• Upward-sloping SRAS curve (labelled AS or SRAS)

• Two downward-sloping AD curves: AD1 (original) shifting right to AD2

• Original equilibrium at PL1 and GDP1

• New equilibrium at PL2 (higher) and GDP2 (higher, assuming below full employment) or PL2 higher with same GDP (at full employment)

• A clear rightward shift of AD - not AS - must be shown

Mark scheme levels:

Level 1 [2 marks]: A correctly labelled AD/AS diagram showing AD shifting right and a higher price level, OR a written explanation of the transmission mechanism (depreciation → competitive exports → net exports increase → AD rises → demand-pull inflation) — but not both together.

Level 2 [4 marks]: Both the diagram AND the written explanation. Incorrect diagram labelling caps the mark at [3].

Note on mark allocation: This question has a different level structure from most [4] questions in Paper 3. Level 1 gives 2 marks (not 1–2), and Level 2 gives 4 marks (not 3–4). This means a student with only the diagram OR only the explanation cannot score more than [2]. Getting to [3] or [4] requires both elements together.

Common errors: Shifting AS instead of AD (a depreciating dollar does not immediately change domestic production costs - the cost-push story would come from higher import costs for inputs, but the question specifically asks about demand-pull). Drawing the SRAS curve shifting leftward. Drawing AD shifting leftward. Not connecting the exchange rate movement to the (X − M) component of AD. Writing the explanation without drawing the diagram.

Lawrence's notes: The word "may" in the question is very relevant. Dollar depreciation does not guarantee demand-pull inflation. If the economy is already at full employment, the AD shift produces more inflation and less output expansion. If the Marshall-Lerner condition is not satisfied (the combined elasticities of demand for exports and imports sum to less than one), the trade balance may actually worsen initially after depreciation. The J-curve effect also suggests that in the short run, depreciation may initially widen the trade deficit before it narrows. A strong response acknowledges one of these qualifications - hence the "may" - but the core argument (depreciation → net exports rise → AD rises → demand-pull inflation) is the required content.

Question 1(b) - Recommend a Policy to Correct the USA's Persistent Current Account Deficit (Without Forex Intervention) [10 marks]

Command term: Recommend - present an advisable course of action with appropriate supporting evidence and reasoning in relation to a given situation, problem, or issue.

The limitations: The question explicitly rules out "intervention in foreign exchange markets." This means managed exchange rate depreciation, official reserves management, and currency pegging are not valid answers. Students must select a different mechanism.

Lawrence's notes: The problem context: The USA ran a trade deficit of USD 819 billion in 2023 (down from USD 951 billion in 2022). The main factors identified in the text are: high labour costs, labour unions, and skills shortages in STEM. These are structural, supply-side weaknesses rather than cyclical. The quarterly data in Table 2 shows a persistent deficit across all four quarters with no improvement trajectory. Figure 1 showed the dollar already depreciated 3.4% against the CNY in late 2023, yet the deficit remained large.

Possible policies (mark scheme):

Expenditure switching policies (tariffs, quotas, export subsidies) | Expenditure reducing policies (contractionary fiscal or monetary policy) | Supply-side policies (education and training, investment in STEM, tax incentives for exporters) | Any other valid policy

Mark band analysis: (Five-band rubric - same as all Paper 3 10-mark questions)

Worked example - supply-side policy (investment in STEM education and training):

When addressing the USA's structural current account deficit, the most appropriate long-term policy is a supply-side strategy focused on investment in STEM education and workforce training. The text directly identifies "skills shortages in STEM" as one of three structural causes of the trade deficit alongside high labour costs and labour unions. This signals that the deficit is not primarily cyclical (caused by excess domestic demand) but largely structural - the USA is losing export competitiveness in the high-value, high-technology sectors where the USA's comparative advantage should be the strongest.

Supply-side policies targeting STEM skills aim to increase the productive capacity and international competitiveness of US industries. Government investment in STEM education at secondary and tertiary levels, targeted retraining programmes for workers displaced from declining industries, R&D tax credits for technology firms, and subsidies for apprenticeships in engineering and computing would all increase the human capital base of the economy. Over time, this raises labour productivity, reduces unit labour costs (addressing the "high labour costs" problem identified in the text), and makes US-manufactured goods more price-competitive on world markets.

The mechanism works through the current account. Improved competitiveness → US exports increase (X rises) → imports are partially substituted by domestic production (M falls) → net exports (X − M) improve → current account deficit narrows. This can be shown with a shift of the SRAS curve rightward (lower unit costs for a given price level), combined with improved export volumes.

Let's relate all this to the data: the USA's Q4 2023 trade deficit was USD 195 billion in a single quarter. The 2023 annual deficit fell from USD 951 billion to USD 819 billion - a USD 132 billion improvement - partly due to dollar depreciation. Supply-side policies could accelerate this trend by addressing the underlying competitiveness gap rather than relying on exchange rate movements that the government has been told it cannot manage directly.

The key limitation is time: supply-side education and training policies have very long implementation lags. Improving STEM education takes years to produce a more skilled workforce; the current account will not respond to university curriculum changes in the short term. This is a structural fix for a structural problem, and policymakers cannot expect quick results. A complementary short-term measure - such as targeted export subsidies for US manufacturers - might be needed to bridge the gap while the supply-side improvements take effect.

A second limitation concerns the WTO framework: if export subsidies are used alongside STEM investment, trading partners (including China) may regard them as unfair trade practices and retaliate with tariffs, potentially worsening rather than improving the current account. The text notes that US-China trade is already "characterised by tariffs and retaliatory measures," suggesting this risk is real and current.

On balance, implementing supply-side policies seems the most logical recommendation because they address the root structural causes identified in the text, are consistent with the constraint against forex intervention, and avoid the welfare losses associated with protectionist expenditure-switching policies.

Worked example - expenditure-switching: tariffs:

An expenditure-switching policy - specifically, tariffs on imports from China - could reduce the trade deficit by making Chinese goods relatively more expensive for American consumers, shifting demand towards domestically produced substitutes. The text notes that China is the USA's largest trading partner and that trade relations are already characterised by tariffs and retaliatory measures, indicating this policy has already been partially implemented. Additional tariffs on strategic goods (semiconductors, steel, electric vehicles) could further widen the price gap between imports and domestic alternatives.

The limitation here is the risk of retaliation. China could impose equivalent tariffs on US exports, reducing the net improvement in the current account. The text's reference to "retaliatory measures" confirms this is not just theoretical risk. Additionally, tariffs raise prices for domestic consumers, creating a welfare loss (a deadweight loss triangle in the consumer surplus diagram), which mainly affects lower-income households generating further inequality. The overall current account improvement from tariffs also depends on the price elasticity of demand for imports: if US demand for Chinese goods is inelastic (few domestic substitutes available in the short run), higher prices do not significantly reduce import volumes and the trade balance may worsen.

Question 2 - Indonesia: Comparative Advantage, Palm Oil, Income Inequality, and Carbon Emissions

The context for Question 2 was Indonesia, a middle-income Southeast Asian country. The question covered two interconnected challenges: the economic and environmental costs of palm oil production (comparative advantage theory, negative production externalities, and the socially optimal output), and Indonesia's income inequality (Lorenz curve construction) and carbon emissions (fuel subsidy welfare loss, followed by a 10-mark policy recommendation). The breadth of this question - spanning international trade theory, welfare economics, income distribution, and environmental economics - makes it one of the most syllabus-extensive single Paper 3 question in recent years.

Question 2(a)(i) - Determine Comparative Advantage in Coffee [2 marks]

Command term: Determine - obtain the answer using the data and show the process.

What the question asked: Using Table 3, determine which country has a comparative advantage in producing coffee.

Table 3 data:

Indonesia: produces 15 kg palm oil OR 20 kg coffee per hour

Malaysia: produces 10 kg palm oil OR 10 kg coffee per hour

Method - opportunity cost of producing 1 kg of coffee:

Indonesia: to produce 1 kg of coffee, must sacrifice 15/20 = ¾ kg of palm oil

Malaysia: to produce 1 kg of coffee, must sacrifice 10/10 = 1 kg of palm oil

Answer: Indonesia has a lower opportunity cost for coffee (¾ palm oil vs 1 palm oil). Therefore Indonesia has a comparative advantage in coffee production.

Mark scheme: [1] for correctly using the data to show Indonesia has a lower opportunity cost or is relatively more efficient in coffee. [1] for stating Indonesia has comparative advantage in coffee. The calculation and conclusion are two separate marks.

Lawrence's notes: Note on absolute advantage: Indonesia also has absolute advantage in coffee (20 > 10). However, comparative advantage is determined by opportunity cost, not absolute output. Even though Indonesia can produce more of both goods per hour than Malaysia, it should specialise in coffee because its relative disadvantage in palm oil is smaller. Malaysia's opportunity cost for palm oil is 10/10 = 1 coffee; Indonesia's opportunity cost for palm oil is 20/15 = 1.33 coffee - so Malaysia has comparative advantage in palm oil. Each country specialises in the good where it has the lower opportunity cost.

Common errors: Confusing absolute advantage with comparative advantage and concluding that Indonesia should specialise in both goods (impossible). Calculating the opportunity cost of palm oil rather than coffee. Stating Indonesia has comparative advantage without showing the opportunity cost calculation - this earns [1] not [2].

Question 2(a)(ii) - Sketch PPC Diagrams for Indonesia and Malaysia [2 marks]

Command term: Sketch - draw a clearly labelled diagram; precision of scale less important than structure.

What the question asked: Using Table 3 and assuming constant costs, sketch the PPCs for Indonesia AND for Malaysia on the same diagram.

Constant costs:

The assumption of constant opportunity costs means the PPC is a straight line (linear), not the typical concave (bowed outward) PPC. This is because the opportunity cost of switching from one good to the other does not increase as more of one good is produced.

Diagram requirements:

• Y-axis: Coffee (kg), X-axis: Palm oil (kg) - or reversed (mark scheme accepts both)

• Indonesia's PPC: straight line from (0, 20) on the coffee axis to (15, 0) on the palm oil axis. Label: Indonesia

• Malaysia's PPC: straight line from (0, 10) on the coffee axis to (10, 0) on the palm oil axis. Label: Malaysia

• Both lines correctly intercept at their respective maximum output values

• Indonesia's PPC lies outside Malaysia's on both axes (Indonesia has absolute advantage in both goods)

• The slopes of the two lines are different - Indonesia's slope is steeper in coffee terms, reflecting its comparative advantage there

Mark scheme levels:

Level 1 [1 mark]: A diagram with palm oil and coffee on the axes AND either two labelled straight lines without correct intersections, OR two labelled curved lines with correctly denoted intersections.

Level 2 [2 marks]: A fully labelled diagram with palm oil and coffee on the axes, two straight lines, correctly labelled Indonesia and Malaysia, with the correct intersections (Indonesia: 20 coffee / 15 palm oil; Malaysia: 10 coffee / 10 palm oil).

Common errors: Drawing curved (concave) PPCs - the question specifies constant costs, which means straight lines only. Plotting the intersections incorrectly (e.g., swapping palm oil and coffee figures). Drawing both lines with the same slope (which would imply equal opportunity costs and no basis for trade). Forgetting to label which line belongs to which country.

Question 2(a)(iii) - Two Reasons Against Specialisation for Indonesia [4 marks]

Command term: Explain - give a clear account of each reason, showing the mechanism.

Mark scheme levels:

Level 1 [1–2 marks]: One reason stated [1]. Two reasons stated OR one reason explained [2].

Level 2 [3–4 marks]: One reason explained AND one reason stated [3]. Two reasons explained [4].

Creditable reasons (from mark scheme) with full explanations:

Palm oil provides food security for low-income households: The text states that Indonesia's palm oil industry provides cheap cooking oil for low-income households. If Indonesia fully specialises in coffee (its comparative advantage) and imports all its palm oil from Malaysia, it becomes dependent on a trading partner for a staple food. Price volatility in palm oil international markets, supply disruptions, or geopolitical tensions with Malaysia could leave Indonesian low-income households facing a sudden, sharp rise in the price of a basic necessity. This is a food security argument against full specialisation that comparative advantage theory ignores.

Costs are not necessarily constant - deforestation and resource depletion: The theory assumes constant opportunity costs (hence the straight-line PPC). In reality, as Indonesia expands coffee production, it faces increasing opportunity costs because the best coffee-growing land is used first and progressively less suitable land must be cleared. Deforestation for coffee or palm oil plantations also destroys carbon-rich tropical forests, generating substantial external costs that the comparative advantage model ignores. The model's assumption of constant costs does not hold.

Resources within Indonesia are not perfectly mobile between sectors: Comparative advantage assumes that labour and capital can move freely from palm oil production to coffee production as specialisation occurs. In practice, workers in palm oil plantations cannot simply become coffee farmers without retraining, and the physical capital (harvesting equipment, palm oil refineries) cannot be converted to coffee processing. This leads to structural unemployment in the declining sector and transitional costs that the theory ignores.

Transport costs not included: The theory assumes costless trade. If Indonesia exports coffee to Malaysia and imports palm oil, the transport costs across the distances involved may exceed the efficiency gains from comparative advantage, making trade disadvantageous for both countries.

Primary commodity vulnerability: Both coffee and palm oil are primary products subject to price volatility driven by weather, disease, and global demand shifts. Specialising in a single primary commodity - even one where comparative advantage exists - exposes Indonesia to commodity price shocks. A fall in global coffee prices would devastate an economy that has fully specialised in coffee, with few economic buffers.

Trade barriers and geopolitical risk: The theory assumes free trade. In practice, Malaysia could impose export tariffs on palm oil, and third-country tariff barriers could restrict Indonesia's coffee exports. The text references how US-China trade is characterised by tariffs and retaliatory measures - the same risks apply to Indonesia-Malaysia agricultural trade.

Common errors: Restating the comparative advantage theory rather than explaining reasons against it. Giving one well-explained reason and four brief statements - only the best two count, but a shallow fourth reason will not compensate a full explanation of a second reason. Saying "specialisation might not work" without explaining the mechanism through which it fails.

Question 2(a)(iv) - Outline Why Palm Oil Market Is Not Perfectly Competitive [2 marks]

Command term: Outline - give a brief account using evidence from Table 4.

Mark scheme levels:

Level 1 [1 mark]: A vague statement that the firm has market power, OR the price changes as output changes, OR the demand curve slopes down, OR MR is lower than price/AR - without including data from Table 4.

Level 2 [2 marks]: The same idea AND supporting evidence from Table 4. For example: "At 3 kg, P = 20, while at 4 kg, P = 18 - in perfect competition, a single firm faces a horizontal demand curve and price does not change with output." OR "At 4 kg, MR = 12 while P = 18 - in perfect competition, MR = AR = P."

Calculating MR at Q = 4: TR at Q = 3 is 60, TR at Q = 4 is 72. MR = (72 − 60) ÷ 1 = 12. Price at Q = 4 is 18. Since MR (12) < Price (18), the firm is a price-maker, not a price-taker. In perfect competition, MR = AR = price. This firm's MR falls below price, which means it faces a downward-sloping demand curve - a characteristic of imperfect competition (monopoly, oligopoly, or monopolistic competition).

Alternative approach: Identify the relationship [1] (price falls as output increases) AND explain why this relationship shows non-perfect competition [1] (in perfect competition, firms are price-takers and face a horizontal demand curve at the market price - price does not fall with output for a single firm).

Common errors: Stating that the market is not perfectly competitive without using data from Table 4 - this earns only [1]. Confusing total revenue with marginal revenue. Identifying the externality (MSC > MPC) as the reason for non-perfect competition - this is market failure, not imperfect competition. The non-perfect competition point is about price-setting power, not about the externality.

Question 2(a)(v) - Calculate Profit at 3 kg [1 mark]

Command term: Calculate - TR − TC.

Worked answer:

Profit = TR − TC = 60 − 6 = 54 (thousand IDR)

Mark scheme: An answer of 54 or 54,000 IDR without working earns [1].

Context note: The table does not give the profit figure for Q = 3 (marked as "-"). All other profit figures are given. This question tests the most basic formula. At Q = 7, profit is 74 thousand IDR - the highest in the table, which means Q = 7 is the firm's profit-maximising level of output (where MR = MC). However, the socially optimal output (where MSB = MSC) is lower, as addressed in question (vii).

Question 2(a)(vi) - Calculate Marginal Private Cost (7 kg to 8 kg) [1 mark]

Command term: Calculate - ΔTC ÷ ΔQ.

Worked answer:

MC = ΔTC ÷ ΔQ = (25 − 17) ÷ 1 = 8 (thousand IDR)

Mark scheme: An answer of 8 or 8,000 IDR without working earns [1]. The MC column in Table 4 has a "-" for the 8 kg row - this is the missing value that students must calculate.

Lawrence's notes: The MC at Q = 8 is 8 thousand IDR, but the MSC at Q = 8 is 22 thousand IDR (given in Table 4). This confirms the presence of a substantial negative externality: external cost = MSC − MPC = 22 − 8 = 14 thousand IDR per kg. The question text states that the external cost (included in MSC) is IDR 14,000 per unit - consistent with this calculation. This external cost represents the environmental damage from deforestation associated with each additional kilogram of palm oil produced.

Question 2(a)(vii) - Identify Output Level When Social Surplus Is Maximised [1 mark]

Command term: Identify - locate the relevant output level from the data in Table 4.

Principle: Social (community) surplus is maximised at the socially optimal output - where MSB = MSC. At this point, the last unit produced adds exactly as much to social benefit as it costs society. Below this output, MSB > MSC (there are unrealised gains from production); above it, MSC > MSB (producing more costs society more than the benefit received).

Reading Table 4:

Q = 4: MSB = 18, MSC = 15 → MSB > MSC → more should be produced (net social benefit from producing)

Q = 5: MSB = 16, MSC = 16 → MSB = MSC → social optimum - social surplus maximised here

Q = 6: MSB = 14, MSC = 17 → MSB < MSC → over-production (net social cost from producing more)

Answer: 5 kg

Mark scheme: An answer of 5 or 5 kg earns [1]. No working required.

Lawrence's notes: The text states that when the firm cuts output from its profit-maximising level (Q = 7, profit = 74) to the socially optimal level (Q = 5, profit = 71), the fall in profit is only 4.05%. Let's verify: (74 − 71) ÷ 74 × 100 = 3 ÷ 74 × 100 = 4.05%. This matches the text precisely and confirms Q = 5 is the socially optimal output. The World Bank's argument - that tropical forests can be protected with only a small reduction in profit - is quantitatively supported by this data.

Common errors: Identifying Q = 7 (profit-maximising output where MR = MC) rather than Q = 5 (socially optimal output where MSB = MSC). These two levels of output test different concepts: Q = 7 maximises private profit; Q = 5 maximises social welfare. The distinction is the entire point of the negative externality analysis.

Question 2(a)(viii) - Construct Lorenz Curve for 2000 on Figure 2 [2 marks]

Command term: Construct - plot the curve using data from Table 5.

What the question asked: Add the 2000 Lorenz curve to Figure 2, which already shows the 2022 curve.

Calculating cumulative income shares for 2000:

Bottom 20% of households: 10% of income → plot point (20, 10)

Bottom 40% of households: 10 + 14 = 24% of income → plot point (40, 24)

Bottom 60% of households: 24 + 16 = 40% of income → plot point (60, 40)

Bottom 80% of households: 40 + 22 = 62% of income → plot point (80, 62)

All households: 100% of income → plot point (100, 100)

Mark scheme: [1] for a curve (smooth or using straight lines between points) accurately plotted at the 20th and 60th percentile points (10% and 40% income respectively) with other points approximately correct - but without a label. [2] for the same, labelled "2000."

What the curves show: The 2000 Lorenz curve should sit closer to the line of equality (diagonal) than the 2022 curve - inequality was lower in 2000 (Gini = 0.295) than in 2022 (Gini = 0.379, given in Table 6). The 2022 curve is more bowed outward, reflecting greater concentration of income at the top. By 2022, the highest 20% held 46% of income (versus 38% in 2000). The 2000 curve being closer to the line of equality visually confirms what the Gini data shows numerically.

Common errors: Plotting the 2000 curve outside (further from the line of equality than) the 2022 curve - this is wrong because 2000 had less inequality than 2022. Forgetting to label the curve "2000." Using the 2022 income shares instead of the 2000 shares from Table 5. Not starting the curve from (0, 0) and ending at (100, 100).

Question 2(a)(ix) - Two Possible Causes of Income Inequality in Indonesia [4 marks]

Command term: Explain - give a clear account of each cause, showing the mechanism.

Mark scheme levels:

Level 1 [1–2 marks]: One cause stated [1]. Two causes stated OR one cause explained [2].

Level 2 [3–4 marks]: One cause explained AND one cause stated [3]. Two causes explained [4].

Creditable causes (from mark scheme) with full explanations:

Different levels of human capital and access to education: Indonesia is a geographically dispersed archipelago of over 17,000 islands. Access to quality education varies dramatically between urban centres (Jakarta, Surabaya) and rural and remote communities. Households in rural areas have less access to trained teachers, better schools, and tertiary education - so their children accumulate less human capital, earn lower wages, and perpetuate intergenerational poverty. This is reflected in Table 5: the bottom 20% of households earned only 10% of income in 2000 and even less (7%) by 2022, suggesting that educational and skills gaps have widened with economic growth.

Unequal ownership of capital: Palm oil production in Indonesia is highly capital-intensive. Large plantation owners and agribusiness corporations own the land and capital equipment; smallholder farmers and plantation workers own little capital and primarily earn wages. As the palm oil industry grows - driven by comparative advantage and export demand - capital owners accumulate profits disproportionately, increasing the income share of the highest quintile (from 38% in 2000 to 46% in 2022) while the share of the bottom quintile falls (from 10% to 7%).

Globalisation and structural change: Indonesia's integration into global agricultural supply chains (palm oil exports to the EU, India, China) has benefited exporters and landowners but displaced smallholder farmers whose land was absorbed into larger plantations. Workers who lose traditional livelihoods to export-led agribusiness expansion may face structural unemployment - they cannot quickly transition to new sectors - worsening income distribution.

Inequality of opportunity - regional and ethnic disparities: Place of birth and parental background strongly predict income in Indonesia. Urban households in Java (where most economic activity is concentrated) have systematically higher incomes than rural households in Sulawesi, Kalimantan, or Papua. Ethnic minorities and indigenous communities often lack formal land rights, preventing them from participating in the economic gains from resource extraction.

Corruption - diversion of redistribution funds: Indonesia ranks moderately on corruption perception indices. Funds allocated for social transfers, infrastructure in remote regions, and educational investment can be diverted through corruption, preventing redistribution from reaching low-income households. This perpetuates inequality even when progressive government policy is nominally in place.

Common errors: Stating broad causes without explaining the mechanism through which they generate inequality. Using examples from countries other than Indonesia. Giving more than two causes without explaining any - only the best two are assessed. Confusing the causes of inequality with its effects (e.g., saying "inequality causes poverty" rather than identifying what drives the unequal distribution in the first place).

Question 2(a)(x) - Calculate Total Welfare Loss from the Subsidy (Figure 3) [1 mark]

Command term: Calculate - read values from the diagram and apply the triangle area formula.

Reading Figure 3:

The market price with the subsidy is given as IDR 5,000 per litre (= 5 on the y-axis, in 1,000 IDR units).

Reading from the diagram: where the subsidised supply curve (S with subsidy) intersects D, the quantity is approximately 1.5 million litres at P = 5,000 IDR.

The free-market equilibrium (where S intersects D, without subsidy) is at approximately Q = 1.25 million litres and P = 6,000 IDR.

At Q = 1.5 million litres (with subsidy), the supply curve without subsidy reads approximately 7,000 IDR. This means the subsidy per unit = 7,000 − 5,000 = 2,000 IDR per litre.

Welfare loss formula:

Welfare loss (deadweight loss) from a subsidy = ½ × change in quantity × subsidy per unit

= ½ × (1.5 − 1.25) × (7 − 5)

= ½ × 0.25 × 2

= 0.25 billion IDR

Units check: 0.25 million litres × 2,000 IDR/litre = 500,000,000 IDR = IDR 0.5 billion ÷ 2 = IDR 0.25 billion

Mark scheme: An answer of 0.25 (billion) IDR without working earns [1].

Lawrence's notes:

Conceptual note - why does a subsidy create welfare loss? The free-market equilibrium (Q = 1.25, P = 6,000) maximises total surplus. The subsidy artificially lowers the consumer price to IDR 5,000 and increases consumption to Q = 1.5 million litres. But between Q = 1.25 and Q = 1.5, the social cost of producing each additional litre (read from the unsubsidised supply curve, starting at 6,000 and rising to 7,000 IDR) exceeds the social benefit (read from the demand curve, falling from 6,000 to 5,000 IDR). The government is paying for production that costs society more than it is worth - the welfare loss triangle represents these inefficient transactions. This is why removing the fossil fuel subsidy and replacing it with cash transfers is argued to be welfare-improving.

Common errors: Calculating the total government cost of the subsidy (2,000 × 1.5 million = IDR 3 billion) rather than the welfare loss (the triangular deadweight loss). Using the wrong base or height for the triangle. Reading the graph incorrectly and getting different values for the equilibrium points.

Question 2(b) - Recommend a Policy to Reduce Carbon Emissions in Indonesia [10 marks]

Command term: Recommend - present a recommended course of action with appropriate supporting evidence and reasoning in relation to a given situation, problem, or issue.

The problem context: Indonesia's carbon dioxide emissions per capita rose from 1.19 tons in 2000 to 2.48 tons in 2022 (Table 6) - a 108% increase, despite moderate GDP per capita growth. Sources identified in the question include: fossil fuel subsidies (currently being phased out), palm oil deforestation, coal-generated electricity (most electricity generation), low carbon tax (USD 2.10 per tonne - far below the social cost of carbon), insufficient renewable energy investment, and low car ownership (10%) meaning most transport emissions come from motorbikes and public transport. The Gini coefficient data shows that income inequality is a live concern, which means any policy must be assessed for its distributional impact.

Possible policies (mark scheme list):

Moving resources to coffee instead of palm oil | Reducing deforestation through improved land use regulation | Cutting palm oil production to socially optimal level | Investment in renewable energy (funded by subsidy savings) | Carbon pricing or taxes on petrol with revenue for public transport | Removing fuel subsidies and replacing them with targeted cash transfers | Subsidies for electric vehicles | Improving public transport and cycling infrastructure | Tax breaks for hybrid or electric vehicles | Education and green nudges | Any other valid policy

Mark band analysis: (Same five-band rubric as all Paper 3, 10-mark questions)

Worked example - carbon tax (Pigouvian tax) with revenue recycling:

The following recommendations make economic sense in order to reduce Indonesia's carbon emissions. An increased carbon tax on fossil fuels, combined with "revenue recycling" or redirecting the income collected from this tax to generate cash transfers for low-income households and finally, investment in renewable energy. The text explicitly states that Indonesia's current carbon tax of USD 2.10 per tonne is insufficient to have a significant market impact - so the case for a higher tax is directly supported by the evidence provided.

Carbon emissions from palm oil deforestation and coal-fired electricity generation are negative production externalities. As Table 4 shows, the firm's marginal social cost (MSC) substantially exceeds its marginal private cost (MPC): at Q = 5 kg, MSC = 16 while MPC = 2 - the external cost is IDR 14,000 per unit. A Pigouvian tax set equal to the external cost per unit of carbon emitted would internalise this externality, shifting the supply curve upward (supply with carbon tax is equivalent to a higher effective MPC) until the market equilibrium moves to the socially optimal output (Q = 5 in the palm oil example).

The quantitative case is compelling. Table 4 shows that reducing palm oil output from the profit-maximising level (Q = 7) to the socially optimal level (Q = 5) causes a fall in profit of only 4.05%. This directly supports the World Bank's argument cited in the text: the largest tropical forests could be protected with only a small reduction in profit. A carbon tax large enough to shift equilibrium from Q = 7 to Q = 5 would achieve this with minimal economic disruption to producers.

The distributional concern is also extremely critical. Indonesia's fuel subsidy currently keeps energy prices low for low-income households (IDR 5,000 per litre rather than IDR 6,000). Removing the subsidy and replacing it with a carbon tax raises prices for all households, including the poorest. Table 5 shows that the bottom 20% already earn only 7% of national income - a regressive carbon tax would worsen this. The solution is revenue recycling: using carbon tax revenue to fund direct cash transfers to low-income households. The text itself supports this: the government is already "gradually replacing subsidies with cash transfer payments" with the aim of reducing both carbon emissions and poverty simultaneously. The carbon tax accelerates and extends this transition.

The welfare loss analysis from Figure 3 also supports this recommendation. The current subsidy generates a deadweight loss of IDR 0.25 billion. Removing the subsidy eliminates this welfare loss, and a carbon tax above the market price further corrects the negative externality - a double dividend: efficiency gain from removing the subsidy plus environmental gain from the carbon tax signal.

The main limitation of a carbon tax in Indonesia's context is how ineffective the current baseline carbon tax is: USD 2.10 per tonne is far below the social cost of carbon estimated by most researchers (typically USD 50–200 per tonne). A meaningful increase would require political willingness to oppose coal producers and large palm oil conglomerates. Additionally, if Indonesia raises its carbon tax unilaterally while trading partners do not, Indonesian palm oil and coal-based products become relatively more expensive on global markets, potentially reducing export competitiveness - a huge concern given Indonesia's comparative advantage in agricultural exports.

On balance, a carbon tax with revenue recycling is the strongest recommendation because: it directly addresses the market failure (negative externality); it is supported by data from Table 4 (the 4.05% profit reduction at socially optimal output) and Table 6 (rising emissions despite growth); it aligns with the government's existing historical record of subsidy removal and cash transfers; and it addresses both the environmental and equity objectives simultaneously.

Worked example - removing fuel subsidies and investing in renewable energy:

An alternative economic policy is to remove remaining fossil fuel subsidies completely and redirect the fiscal savings into subsidised investment in renewable energy sources. The text already notes that "removing subsidies completely would release funds for government spending on health and education" - renewable energy investment is an equally valid use of those freed funds. Table 6 shows that despite annual GDP per capita growth averaging 4%+, carbon emissions per capita rose from 1.19 to 2.48 tonnes - and economic growth has benefited from emissions, because most electricity is generated from low-cost coal. Subsidised investment in solar, geothermal (Indonesia sits on the Pacific Ring of Fire and has enormous geothermal potential), and wind energy would shift the electricity generation mix away from coal, reducing the carbon intensity of economic growth.

The limitation is fiscal: renewable energy infrastructure requires large upfront capital investment. Indonesia's budget constraints and high existing debt levels may limit the scale of this programme without international climate finance (e.g., from the World Bank or Green Climate Fund). The 10% car ownership rate cited in the text also suggests that the biggest emissions reductions come from the electricity and industrial sectors rather than personal transport - making grid-level renewable investment more impactful than, say, electric vehicle subsidies.

Quick Reference: What Came Up in IB Economics Paper 3 November 2025

Question 1 (USA economy): Real GDP growth rate calculation | Real interest rate calculation | How commercial banks create money | Defining and outlining quantitative easing | Money market diagram (increase in money supply → fall in interest rate) | Balance of trade in goods and services (Q3) | Financial account calculation using BOP identity (Q4) | Percentage change in USD/CNY exchange rate from graph | AD/AS diagram: dollar depreciation and demand-pull inflation | 10-mark recommend: policy to correct the USA's persistent current account deficit without forex intervention

Question 2 (Indonesia): Comparative advantage in coffee - opportunity cost method | PPC sketch for two countries with constant costs | Two reasons against specialisation for Indonesia | Why palm oil market is not perfectly competitive (from data) | Profit at Q = 3 kg | Marginal private cost (MC) from Q = 7 to Q = 8 | Socially optimal output where MSB = MSC | Construct Lorenz curve for 2000 on Figure 2 | Two causes of income inequality in Indonesia | Welfare loss from fossil fuel subsidy calculation | 10-mark recommend: policy for Indonesia to reduce carbon emissions

Key syllabus areas: National income accounting (GDP growth rate) | Real versus nominal interest rates | Money creation and the money multiplier | Quantitative easing | The money market diagram | Balance of payments (current account, capital account, financial account) | Exchange rate percentage change | AD/AS model and demand-pull inflation | Comparative advantage and opportunity cost | Production possibility curves | Limits of free trade theory | Negative production externalities and social cost | Socially optimal output (MSB = MSC) | Lorenz curve construction and income inequality | Welfare loss from a subsidy | Carbon tax as a Pigouvian tax

Calculations tested: GDP growth rate ((GDP₁ − GDP₀) ÷ GDP₀ × 100) | Real interest rate (nominal - inflation) | Balance of trade (X − M) | Financial account (negative of current + capital account) | Exchange rate percentage change | Opportunity cost from production data | Profit (TR − TC) | Marginal private cost (ΔTC ÷ ΔQ) | Welfare loss triangle (½ × Δquantity × subsidy per unit) | Identifying socially optimal output from MSB/MSC table

Frequently Asked Questions: IB Economics Paper 3 November 2025

What topics came up in IB Economics HL Paper 3 November 2025?

IB Economics HL Paper 3 November 2025 covered two compulsory questions. Question 1 used the United States economy as context and tested GDP growth rate calculation, real interest rate calculation, money creation by commercial banks, quantitative easing, the money market diagram, balance of trade and financial account calculations from quarterly balance of payments data, exchange rate percentage change from a graph, and an AD/AS diagram linking dollar depreciation to demand-pull inflation, concluding with a 10-mark recommend question on policies to correct the USA's current account deficit without foreign exchange market intervention.

Question 2 used Indonesia as context and tested comparative advantage through opportunity cost calculation, production possibility curves with constant costs, limitations of the comparative advantage model, negative externalities in the palm oil market, profit and marginal cost calculations from a data table, identifying the socially optimal level of output, constructing a Lorenz curve from income distribution data, causes of income inequality, calculating welfare loss from a subsidy diagram, and a 10-mark recommend question on reducing carbon emissions in Indonesia.

How do you calculate the financial account in IB Economics Paper 3?

The financial account is calculated using the balance of payments identity: current account + capital account + financial account = 0. Therefore, financial account = −(current account + capital account). In the November 2025 Paper 3, the Q4 current account was calculated as (1180 − 1375) + 36 + (−39) = −198 USD billion, and the capital account was −2 USD billion. The financial account = −(−198 + (−2)) = +USD 200 billion. A financial account surplus means the USA was receiving net capital inflows - foreigners were buying US assets - which finances the current account deficit.

How do you determine comparative advantage in IB Economics?

Comparative advantage is determined by comparing opportunity costs, not absolute output. Calculate the opportunity cost of producing one unit of each good for each country by dividing what must be given up. In the November 2025 Paper 3, Indonesia's opportunity cost of 1 kg of coffee = 15/20 = ¾ kg of palm oil, while Malaysia's opportunity cost of 1 kg of coffee = 10/10 = 1 kg of palm oil. Since Indonesia's opportunity cost for coffee is lower (¾ < 1), Indonesia has a comparative advantage in coffee. The country that gives up less of the other good to produce one unit, has comparative advantage in that good.

How do you identify socially optimal output in IB Economics?

The socially optimal output is where marginal social benefit (MSB) equals marginal social cost (MSC). This is the output level that maximises total social (community) surplus. In the November 2025 Paper 3 Table 4, MSB equals MSC at Q = 5 kg of palm oil: both MSB and MSC equal 16 thousand IDR. At outputs below 5 kg, MSB exceeds MSC - society gains from more production. At outputs above 5 kg, MSC exceeds MSB - each extra unit costs society more than it is worth. This is distinct from the profit-maximising output (Q = 7, where MC = MR), which is higher because private costs understate social costs due to the negative externality of deforestation.

How do you construct a Lorenz curve in IB Economics?

A Lorenz curve plots the cumulative percentage of income (y-axis) against the cumulative percentage of households ranked by income (x-axis). Start by converting the income shares of each quintile into cumulative totals. For Indonesia's 2000 data: the bottom 20% hold 10% of income → plot (20, 10); the bottom 40% hold 10 + 14 = 24% → plot (40, 24); the bottom 60% hold 24 + 16 = 40% → plot (60, 40); the bottom 80% hold 40 + 22 = 62% → plot (80, 62); and all households hold 100% → plot (100, 100). Connect the points with a smooth curve or straight lines, starting from the origin (0, 0). The further the curve bows away from the line of perfect equality (the 45-degree diagonal), the more unequal the income distribution.

How do you calculate welfare loss from a subsidy in IB Economics Paper 3?

The welfare loss from a subsidy is the area of the deadweight loss triangle between the free-market equilibrium quantity and the subsidised quantity. The formula is ½ × (change in quantity from subsidy) × (subsidy per unit). In the November 2025 Paper 3 Figure 3, the free-market equilibrium was at approximately 1.25 million litres per year, while the subsidised quantity was 1.5 million litres. The subsidy per unit (the vertical distance between the S and S-with-subsidy curves at the subsidised quantity) was 2,000 IDR per litre (from 7,000 to 5,000 on the supply side). Welfare loss = ½ × 0.25 × 2 = 0.25 billion IDR. Always check whether the question asks for the answer in billions, millions, or absolute IDR values, and ensure units are consistent.

Read More About:

IB Economics Hub Page your IB Economics daily guide

IB Economics Diagrams Page Check this resource for All the IB Economics syllabus diagrams with explanations

IB Economics Paper 1 Hub Page

IB Economics Paper 2 Hub page

IB Economics Paper 3 Hub Page

IB Economics Activity book Page More IB Economics exam practice, activities, model answers and IB Economics Marking schemes

IB Economics HL Hub Page

IB economics Calculations Book 25 units of IB Economics SL and HL calculations exercises, IB model answers, and IB marking schemes

Read Next: IB Economics Exam Paper 3 November 2024