The increase in the demand for a commodity may lead to a decrease in the demand for another if both are

The increase in the demand for a commodity may lead to a decrease in the demand for another if both are in competitive demand. When two goods are in competitive demand, they are seen as substitutes for each other, meaning that they can be used for the same purpose. For example, coffee and tea can be seen as substitutes for each other, since both are beverages that can be used to satisfy the same desire for a hot drink. So, if the demand for coffee increases, people may buy more coffee and less tea, because they see coffee as a substitute for tea. Similarly, if the demand for tea increases, people may buy more tea and less coffee, because they see tea as a substitute for coffee. On the other hand, if two goods are in complementary demand, they are often used together. For example, if the demand for cars increases, the demand for gasoline will also increase, since cars require gasoline to run. Similarly, if the demand for smartphones increases, the demand for phone cases may also increase, since people may want to protect their phones. In composite demand, a good has multiple uses, so an increase in demand for one use may not necessarily lead to a decrease in demand for another use. And in the case of goods of the same quality, an increase in demand for one good does not necessarily affect the demand for the other good, since they are not substitutes or complements.