Which of the following factors is not a cause of change in demand? Changes in

Analyze the question: We are asked to find the factor that is not a cause of a change in demand (that is, not a shift of the demand curve).

Concept: Economics separates two ideas:

• Change in quantity demanded (a movement along the demand curve) is caused only by a change in the price of the commodity itself.
• Change in demand (a shift of the whole demand curve) is caused by non-price factors, called the determinants of demand. These include: • Income and income distribution • Tastes and fashion • Population size • Prices of related goods (substitutes and complements) • Expectations about future prices • Advertising

Check each option:

• A. Size of population: More people means more buyers, so the demand curve shifts. This is a cause of change in demand.
• B. Price of the commodity: This only moves us along the same demand curve, so it changes the quantity demanded, not the demand. This is not a cause of change in demand.
• C. Income distribution: This changes who has purchasing power and so shifts demand. It is a cause.
• D. Taste and fashion: A change in preferences shifts the demand curve. It is a cause.

Answer: The own price of the commodity is the factor that does not cause a change in demand. It causes a change in quantity demanded.

Exam tip: Remember "Price moves along, everything else shifts." If the question mentions the commodity's own price, think of a movement along the curve. If it mentions anything else (income, taste, population, related goods), think of a shift of the curve.