Another factor that influences demand is the price of related goods. The dramatic fall in the price of computers over the past twenty years has significantly increased the demand for printers, monitors and internet access. Such goods are examples of complements. Formally, for a given good X, a complement is a good whose consumption increases the value of X. Thus, the use of computers increases the value of peripheral devices like printers and monitors. The consumption of coffee increases the demand for cream for many people. Spaghetti and tomato sauce, national parks and hiking.
