The prices of complementary or substitute goods also shift the demand curve. When the price of a good that complements a good decreases, then the quantity demanded of one increases and the demand for the other increases.

How do substitutes and complements affect demand?

Substitute goods (or simply substitutes) are products which all satisfy a common want and complementary goods (simply complements) are products which are consumed together. Demand for a product's substitutes increases and demand for its complements decreases if the product's price increases.

What happens when a complement increases?

In economics, a complementary good is a good whose appeal increases with the popularity of its complement. ... If A is a complement to B, an increase in the price of A will result in a negative movement along the demand curve of A and cause the demand curve for B to shift inward; less of each good will be demanded.