TRIBE (DEMAND)

Tastes and preferences

Explanation: Any number of things can suddenly make consumers overall buy more (or less) at every price for a product.

Examples: Celebrity endorsement of a product moves the demand curve for the product to the right. Accusations of fraud shift the demand for an actor's movies to the left. A stern warning from the government about heart disease shifts the demand for fast food to the left.

Related goods and services (price of) 

Explanation: Consumers will be less willing to buy a good at any price level if its substitutes are cheaper. A substitute is a good that people may purchase and use in place of another, like hamburgers instead of hot dogs.

Similarly, consumers will be more willing to buy a good at any price level if any of its complements are cheaper. A complement is a good often bought to use together with another, like hamburger buns for hamburgers.

Examples: If the price for salsa decreases, then the demand for its complement chips will increase at every price level. If the price of one smartphone brand skyrockets, the demand for another popular brand will shift right. If the price of maple syrup goes way up, the demand for its complement pancake mix will decrease. If the price of butter plummets, the demand for its substitute, margarine, will shift left.

Income

Explanation: For some goods, a general increase in consumer income will increase the demand for them; these are called normal goods. For other goods, an increase in consumer income will make consumers demand them less; these are called inferior goods.

Examples: Widespread wage increases in a college town shift the demand for instant noodles (an inferior good) to the left, while the same wage increase causes the demand curve for a pricey coffee shop to shift to the right. (Pricey coffee is a normal good in this market.)


Buyers (number of)

Explanation: If there are more people to demand a good or service, the demand will shift right. If there are fewer people, it will shift left.

Examples: The baby boom after World War II shifted the demand for suburban housing to the right significantly. A city hosting the Super Bowl sees its demand curve for hotels shift dramatically to the right the weekend of the game. A decrease in the number of buyers, such as through a mass emigration out of a country, will shift the demand curve left.

Expectations of price

Explanation: If something leads consumers to believe that the price of a good or service is about to go up, the demand curve will shift right as they buy before they believe it will become more expensive. If they believe the price will soon go down, the demand curve will shift left, as consumers wait to purchase until they believe it will be less expensive.

Examples: After news that a disease has devastated the honeybee population, the demand for honey shifts right as consumers purchase before a possible price increase due to lower availability. A "Black Friday" deal shifts demand to the left for the week before the sale event, as people will wait to buy the item at the lower price.


ROTTEN (SUPPLY)

Resource: Cost and Availability

Explanation: If any resource necessary to produce a good becomes more expensive and/or less available, the supply curve will shift to the left. Likewise, if any necessary resource becomes less expensive and/or more available, the supply curve will shift to the right.

Examples: When fracking made raw oil more accessible, the supply of gasoline shifted to the right and gasoline became less expensive. If a severe frost kills many citrus orchards, the supply curve for orange juice will shift to the left.

Other goods’ prices

Explanation: If suppliers can easily switch to the production of another good that becomes much more profitable, the supply of the good they currently produce will shift left. Similarly, if suppliers cannot make as much producing that other good, the supply curve for the good they originally made will shift back right.

Examples: After the price of California wine increases sharply, increasing its price, the supply curve of avocados shifts left as California farmers replace avocado trees with vineyards. As the price of the cutting-edge generation of video game consoles far exceeds that of the older systems, the older systems' supply curves shift left. When public health concerns shuttered theaters, production companies increased, or shifted right, their supply of content intended for in-home streaming. 


Taxes, subsidies, and government regulation

Explanation: A subsidy will effectively lower the cost of production for producers, shifting the supply curve to the right. A new government regulation or tax will increase the cost of production and shift the supply curve to the left.

Examples: If the American subsidy of the oil industry was reduced, the supply curve would shift to the left and gasoline would be more expensive. Subsidies to higher education in the United States have shifted the supply curve for college and university programs to the right.


Technology (productivity)

Explanation: New productive technology generally has the effect of lowering resource costs, shifting supply to the right. A loss of technology, far less common and often only temporary, can shift supply ot the left.

Examples: Machine harvesters dramatically lowered the cost of the collection and processing of many agricultural products, shifting supply to the right. If you have an antique item, like a typewriter, the supply for repairs will be far to the left—a high price for a very small quantity. Social media sites that collect user data rather than charging a fee for their services have shifted the supply of consumer information to the right. A natural disaster that damages machinery, factories, and shipping trucks over a wide area will decrease supply for a time.


Expectations of the producer

Explanation: If suppliers expect the price they can charge for their respective good or service to increase or decrease, they will adjust production accordingly.

Examples: Every November, the supply of candy canes shifts far to the right as candy companies expect an increase in demand. If a basketball player is forced to resign after a scandal, the supply curve of the player's jerseys will shift to the left as sports apparel companies expect demand for the jerseys to decrease.


Number of firms in the industry

Explanation: If the number of firms in an industry increases, ceteris paribus, the supply will shift to the right. Likewise, a decrease in the number of firms will shift supply to the left.

Examples: As more automotive manufacturers decide to make their own electric car, the supply curve of electric cars shifts to the right. Many record stores are closing each year, shifting the supply curve of music on compact discs (CDs) to the left.