4.1.4 Substitutes and Complements Two goods are substitutes if an increase in the price of one leads to an increase in the quantity demanded of the other. In contrast,two goods are complements if an increase in the price of one leads to a decrease in the quantity demanded of the other❑ Two goods are substitutes if an increase in the price of one leads to an increase in the quantity demanded of the other. In contrast, two goods are complements if an increase in the price of one leads to a decrease in the quantity demanded of the other 4.1.4 Substitutes and Complements