All the following are factors that would bring about a change in supply except

Analyze the question: We are asked which option is NOT a factor that causes a change in supply (that is, a shift of the whole supply curve).

Concept: Change in supply vs. change in quantity supplied

• Change in quantity supplied: This is a movement along the same supply curve. It is caused only by a change in the price of the commodity itself.
• Change in supply: This is a shift of the entire supply curve (right for an increase, left for a decrease). It is caused by factors other than the commodity's own price. These are called the determinants of supply: • Level of technology • Government policy (taxes, subsidies, regulations) • Number of firms in the industry (entry or exit of firms) • Cost of production (wages, raw materials) • Prices of related goods • Weather and natural factors (especially for agriculture) • Producers' expectations

Step-by-step check of the options:

• A. Level of technology: Better technology lowers production costs and shifts supply to the right. It is a determinant of supply.
• B. Government policy: Subsidies increase supply, while taxes reduce it. It is a determinant of supply.
• C. Entry of new firms: More firms mean a larger total output at every price, so the curve shifts right. It is a determinant of supply.
• D. Price of the commodity: A change in the commodity's own price only moves us along the existing supply curve, so it changes the quantity supplied, not the supply itself.

Answer: The factor that does not bring about a change in supply is D. Price of the commodity.

Exam tip: Remember "own price = movement along, everything else = shift." Whenever JAMB asks for an "except" question on supply or demand, check which option is the commodity's own price. That is usually the odd one out.