Which of the following would NOT cause a shift in the demand curve for an agricultural product?

• A. A change in the product's own price.
• B. A change in consumer incomes.
• C. A change in prices of related goods.
• D. A change in tastes and preferences.

Answer: (A)

The key idea is the difference between a movement along the demand curve and a shift of the demand curve. The demand curve shows how quantity demanded responds to price changes, holding other factors constant. A shift happens when non-price factors change overall demand, causing the curve to move left or right. A change in the product’s own price, however, changes only the quantity demanded at that price, so you move up or down the same curve rather than shift it. That’s why a change in the product’s own price does not shift demand.

In contrast, increases in consumer incomes, changes in prices of related goods (substitutes or complements), and changes in tastes and preferences all alter demand itself, shifting the entire curve left or right.