IBonomics2026-W41
Weaknesses in supply–demand shifts and combined diagrams
This week’s aggregate quizzes show strengths on surplus and basic laws, but consistent errors when students must derive market demand or combine multiple supply/demand shocks in one diagram.
Published October 18, 2026
Total quiz attempts
108
Active learners this week
41
Average score
73.9%
Average accuracy (per question)
73.2%
Mean time per question
≈2.6 min
1. Weekly Overview
Supply/demand shifts and diagram synthesis need focused practice.
Aggregate results (n=108 attempts, 41 learners) show an average score near 74%. High accuracy appears on consumer/producer surplus and the basic laws of supply and demand, while multi-step diagram questions (deriving market demand; combining subsidies with changed expectations) have the lowest correct rates and longer completion times.
Student takeaway: Focus next on units 2.1–2.3: practice deriving market demand from individuals and drawing combined supply/demand shift diagrams with clear labels.
2. Key Patterns
Main Insights
Very low accuracy on combined-shock diagrams
The hardest item asked students to show, in one diagram, the effects of a production subsidy plus a large change in expectations for future prices (unit 2.2). Correct rate was 10% and average time was high — a clear sign many are not decomposing multi-shock problems.
Advice: Break the task into steps: (1) label initial equilibrium, (2) draw the effect of the subsidy on supply, (3) draw the effect of changed expectations on demand/supply as specified, (4) identify new equilibrium and compare price/quantity.
Difficulty deriving market demand from individual demand
A medium-difficulty item on deriving market demand from individual demand had a correct rate of 33%, indicating many students misinterpret horizontal aggregation or the role of price in individual schedules (unit 2.1).
Advice: Practice horizontal summation: for each price, add individual quantities to get market quantity; sketch a few price points and connect them to confirm the market curve shape.
Strong understanding of surplus and basic laws
Items on consumer surplus, social surplus and the law of demand had high correct rates (86–93%), showing firm comprehension of welfare concepts and basic demand behaviour (unit 2.3 and 2.1).
Advice: Leverage this strength by practising numerical surplus calculations and using surplus diagrams when analysing policy effects.
Some multi-step equilibrium questions take much longer
A question about how equilibrium price and quantity change when demand increases showed unusually long average time (several hours in aggregate), suggesting students pause to reason through multi-stage changes or return to questions later.
Advice: Timebox multi-step diagram practice (e.g., 20–40 minutes) and check each step; annotate diagrams to make reasoning explicit rather than trying to hold multiple effects in mind.
3. Revision Plan
Priority Areas
Supply shifts & determinants · 2.2
Multiple items on supply shifts and non-price determinants show moderate-to-low accuracy and longer completion times.
Action: Practice short tasks: identify one non-price determinant, state direction of shift, redraw supply curve, and explain price/quantity change in words.
Deriving market demand (horizontal aggregation) · 2.1
Low correct rate on deriving market demand indicates confusion about aggregation.
Action: Work 5–10 problems where you add individual quantities at fixed prices and sketch the resulting market curve.
Combined shocks & diagram synthesis · 2.2 / 2.3
Very low accuracy on multi-shock diagram questions shows difficulty sequencing effects.
Action: Use a 4-step diagram checklist (initial equilibrium → first shock → second shock → compare outcomes) on 6 worked examples.
Equilibrium changes and surplus calculations · 2.3
Good conceptual knowledge exists but some struggle with numerical surplus and combined-policy effects.
Action: Solve a couple of numeric surplus problems and redraw surplus areas after taxes/subsidies to link numbers and graphs.
4. Question Evidence
Featured Questions
Most Wrong Questions
| Question | Topic | Unit | Attempts | Correct | Wrong | Avg Time |
|---|---|---|---|---|---|---|
| In a single diagram for solar panels, show the effects of a government production subsidy and rising expectations that future electricity prices will be much higher. | Microeconomics | 2.2 | 10 | 10.0% | 90.0% | 1.3 min |
| How is market demand derived from individual demand? | Microeconomics | 2.1 | 15 | 33.3% | 66.7% | 18.5 s |
| Which of the following would cause a shift in the supply curve? | Microeconomics | 2.2 | 13 | 46.2% | 53.8% | 19.9 s |
Most Correct Questions
| Question | Topic | Unit | Attempts | Correct | Wrong | Avg Time |
|---|---|---|---|---|---|---|
| What is consumer surplus? | Microeconomics | 2.3 | 14 | 92.9% | 7.1% | 12.1 s |
| According to the law of demand, what happens when the price of a good increases, assuming ceteris paribus? | Microeconomics | 2.1 | 13 | 92.3% | 7.7% | 19.6 s |
| What happens if the price is set below the equilibrium price? | Microeconomics | 2.3 | 16 | 87.5% | 12.5% | 26.4 s |
Most Time Spent Questions
| Question | Topic | Unit | Attempts | Correct | Wrong | Avg Time |
|---|---|---|---|---|---|---|
| What happens to equilibrium price and quantity when demand increases? | Microeconomics | 2.3 | 14 | 64.3% | 35.7% | 98.3 min |
| In IB Economics, how are non-price determinants of supply defined? | Microeconomics | 2.2 | 3 | 100.0% | 0.0% | 16.3 min |
| The UK applies a 20% VAT on clothing purchases, but no indirect taxes are imposed earlier in the fast fashion production process. If the average person in the UK spends £76.53 per month on clothing, estimate the total VAT paid per person annually on clothing. | Microeconomics | 2.7 | 3 | 33.3% | 66.7% | 12.5 min |
5. Conclusion
Practical next steps
Schedule short, focused practice sessions on units 2.1–2.3: do horizontal-aggregation exercises, 6–8 combined-shock diagram problems using the 4-step checklist, and 3 numeric surplus calculations to connect graphs and numbers.
Note: This weekly report is automatically generated and may contain mistakes. Always double-check key points before using them for revision.
Report is based on anonymized aggregate quiz activity (weekly quiz summaries) and does not contain or reveal individual user data.