If two commodities are complements then:

Question

Quizplus · Accepted Answer

Complementary goods have a negative cross-price elasticity, indicating that an increase in the price of one good will lead to a decrease in the quantity demanded of both goods, and vice versa. In contrast, substitute goods have a positive cross-price elasticity, indicating that an increase in the price of one good will lead to an increase in the quantity demanded of the other good, and vice versa. Therefore, the cross-price elasticity of complementary goods will be negative.

If Two Commodities Are Complements Then