Cambridge Syllabus Notes

Demand and Supply Curves

Determinants of Supply

Think of a supply curve like a pizza shop’s menu. The more ingredients (inputs) the shop has, the more pizzas it can make. When the price of cheese (an input) goes up, the shop can’t afford as many pizzas, so the supply shrinks. When the price of cheese drops, the shop can afford more pizzas, so the supply expands. This simple analogy helps you remember the key idea: the cost of inputs is a major determinant of supply. 🍕

Exam Tip: When asked to explain a determinant, always state the direction of the shift (left or right) and give a real‑world example.

Key Determinants of Supply

Price of Inputs – higher input prices shift supply left; lower input prices shift it right.
Technology – better technology shifts supply right (more output for the same input).
Expectations of Future Prices – if producers expect higher future prices, they may hold back supply now, shifting left.
Number of Sellers – more sellers shift the market supply curve right.
Taxes & Subsidies – taxes shift supply left; subsidies shift it right.
Natural Conditions – weather, disease, etc., can shift supply left or right.

Illustration with a Table

Determinant	Effect on Supply Curve	Example
Price of Inputs	↑ → shift left; ↓ → shift right	Oil price falls → more cars produced
Technology	Shift right (more efficient)	Automated assembly line in a factory
Expectations of Future Prices	↑ future → shift left (hold back)	Farmers expect higher wheat prices next year → produce less now
Number of Sellers	More sellers → shift right	New coffee shops open in town
Taxes & Subsidies	Tax ↑ → shift left; subsidy ↑ → shift right	Government subsidy for solar panels → more panels produced
Natural Conditions	Bad weather → shift left; good weather → shift right	Drought reduces crop output

Mathematical Representation

A simple linear supply function is written as:

$Q_s = a + bP$

where $Q_s$ is the quantity supplied, $P$ is the price, $a$ is the intercept, and $b$ (positive) is the slope. A higher $b$ means supply is more responsive to price changes.

Exam Tip: When you see a supply function, identify the slope $b$. If $b$ increases, the supply curve becomes flatter (more elastic). Use the word “elastic” or “inelastic” appropriately in your answer.

Exam Tips for Determinants of Supply

Read the question carefully – does it ask for a cause or an effect?
Use the shift direction (left/right) and price effect (increase/decrease).
Give a specific, real‑world example to show you understand the concept.
When drawing a diagram, label the shift arrow and indicate the new equilibrium if required.
Remember that technology and number of sellers are usually the most straightforward determinants to discuss.
Use the LaTeX notation for equations to show mathematical clarity.
Keep your answer concise but complete – aim for 2–3 sentences per determinant.

determinants of supply