Substitute Goods vs Complementary Goods
Substitute Goods and Complementary Goods are two Supply & Demand concepts in AP Economics that students often mix up. In short: substitute goods is substitute goods are goods that can be used in place of each other to satisfy a particular need or want. Meanwhile, complementary goods is complementary goods are goods that are typically used or consumed together. Here is how they compare side by side.
Substitute goods are goods that can be used in place of each other to satisfy a particular need or want.
When the price of one good increases, the demand for its substitute also increases, as consumers switch to the relatively cheaper alternative. Examples include Coke and Pepsi, or butter and margarine.
Complementary goods are goods that are typically used or consumed together.
When the price of one good increases, the demand for its complement decreases, as consumers buy less of both goods. Examples include cars and gasoline, or printers and ink cartridges.