Increase in income: Consumers use their income to buy products, and the more money they have, the more money they spend. For a normal good, there is a positive relationship between consumer income and the quantity consumed.
Decrease in income. An inferior good is the opposite of a normal good.
Increase in the piercing of a substitute good. When two goods are substitutes, an increase in the price of the first good causes some consumers to switch to the second good.
Decrease in price of a complementary good. When two goods are complements, they are consumed together as a package, and a decrease in the price of one good decreases the cost of the entire package.
Increase in population. An increase in the number of people means there are more individual demand curves to add up to get the market demand curve -so market demand increases.
Shift in consumer preferences.
Expectations of higher future prices.