Demand, Supply and Market Equilibrium
How preferences, income, costs, technology and expectations determine demand and supply, equilibrium price and quantity, shortages and surpluses.
How to study A-level Economics
Define the issue and affected agents, choose an appropriate model, build the causal chain with data, then evaluate assumptions, trade-offs and alternatives before judging.
Core concepts
Concept 1
A price change causes a movement along a demand or supply curve; a non-price determinant shifts the curve.
Exam cue: Identify which curve changes, the direction of the shift and the new equilibrium.
Concept 2
Equilibrium occurs where planned quantity demanded equals planned quantity supplied, given the model's assumptions.
Exam cue: Label axes, original and new curves, equilibrium price and equilibrium quantity.
Concept 3
Market adjustments transmit information and incentives but their speed and outcome depend on context.
Exam cue: Distinguish a temporary disequilibrium from a lasting change in determinants.
Risk pitfalls and guardrails
Shifting demand because the good's own price changes.
Guardrail: Do not substitute a memorised diagram or generic advantage until you have identified the determinant, mechanism, affected agents and time horizon.
Calling demand the same as desire without ability and willingness to pay.
Guardrail: Do not substitute a memorised diagram or generic advantage until you have identified the determinant, mechanism, affected agents and time horizon.
Predicting price change without considering whether both demand and supply shift.
Guardrail: Do not substitute a memorised diagram or generic advantage until you have identified the determinant, mechanism, affected agents and time horizon.
Memory anchors
Demand
Demand is the quantity consumers are willing and able to buy at each price over a period.
Supply
Supply is the quantity producers are willing and able to offer at each price over a period.
Equilibrium
Market equilibrium occurs where quantity demanded equals quantity supplied.
Excess Demand
Excess demand is a shortage at the current price.
Excess Supply
Excess supply is a surplus at the current price.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
The price of coffee falls and consumers buy more coffee, with all other influences unchanged. How is this shown?
Household incomes rise and restaurant meals are a normal good. What is the most likely market effect, other things equal?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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