Substitute good in the context of Pepsi

A monopoly (from Greek μόνος, mónos, 'single, alone' and πωλεῖν, pōleîn, 'to sell') is a market in which one person or company is the only supplier of a particular good or service. A monopoly is characterized by a lack of economic competition to produce a particular thing, a lack of viable substitute goods, and the possibility of a high monopoly price well above the seller's marginal cost that leads to a high monopoly profit. The verb monopolise or monopolize refers to the process by which a company gains the ability to raise prices or exclude competitors. In economics, a monopoly is a single seller. In law, a monopoly is a business entity that has significant market power, that is, the power to charge overly high prices, which is associated with unfair price raises. Although monopolies may be big businesses, size is not a characteristic of a monopoly. A small business may still have the power to raise prices in a small industry (or market).

A monopoly may also have monopsony control of a sector of a market. A monopsony is a market situation in which there is only one buyer. Likewise, a monopoly should be distinguished from a cartel (a form of oligopoly), in which several providers act together to coordinate services, prices or sale of goods. Monopolies, monopsonies and oligopolies are all situations in which one or a few entities have market power and therefore interact with their customers (monopoly or oligopoly), or suppliers (monopsony) in ways that distort the market.

A cost-of-living index is a theoretical price index that measures relative cost of living over time or regions. It is an index that measures differences in the price of goods and services, and allows for substitutions with other items as prices vary.

There are many different methods that have been developed to approximate the cost of living index. A Konüs index is a type of cost-of-living index that uses an expenditure function such as one used in assessing expected compensating variation. The expected indirect utility is equated in both periods.

In economics, a complementary good is a good whose appeal increases with the popularity of another good, its complement. Technically, it displays a negative cross elasticity of demand and that demand for it increases when the price of another good decreases. If ${\displaystyle A}$ is a complement to ${\displaystyle B}$, an increase in the price of ${\displaystyle A}$ will result in a negative movement along the demand curve of ${\displaystyle A}$ and cause the demand curve for ${\displaystyle B}$ to shift inward; less of each good will be demanded. Conversely, a decrease in the price of ${\displaystyle A}$ will result in a positive movement along the demand curve of ${\displaystyle A}$ and cause the demand curve of ${\displaystyle B}$ to shift outward; more of each good will be demanded. This is in contrast to a substitute good, whose demand decreases when its substitute's price decreases.

When two goods are complements, they experience joint demand - the demand of one good is linked to the demand for another good. Therefore, if a higher quantity is demanded of one good, a higher quantity will also be demanded of the other, and vice versa. For example, the demand for razor blades may depend on the number of razors in use; this is why razors have sometimes been sold as loss leaders, to increase demand for the associated blades. Another example is that sometimes a toothbrush is packaged free with toothpaste. The toothbrush is a complement to the toothpaste; the cost of producing a toothbrush may be higher than toothpaste, but its sales depends on the demand of toothpaste.

Independent goods are goods that have a zero cross elasticity of demand. Changes in the price of one good will have no effect on the demand for an independent good. Thus independent goods are neither complements nor substitutes.

For example, a person's demand for nails is usually independent of his or her demand for bread, since they are two unrelated types of goods. Note that this concept is subjective and depends on the consumer's personal utility function.

In economics, the Leontief production function or fixed proportions production function is a production function that implies the factors of production which will be used in fixed (technologically predetermined) proportions, as there is no substitutability between factors. It was named after Wassily Leontief and represents a limiting case of the constant elasticity of substitution production function.

For the simple case of a good that is produced with two inputs, the function is of the form

In microeconomics and consumer theory, a Giffen good is a product that people consume more of as the price rises and vice versa, violating the law of demand.

For ordinary goods, as the price of the good rises, the substitution effect makes consumers purchase less of it, and more of substitute goods; the income effect can either reinforce or weaken this decline in demand, but for an ordinary good never outweighs it. By contrast, a Giffen good is so strongly an inferior good (in higher demand at lower incomes) that the contrary income effect more than offsets the substitution effect, and the net effect of the good's price rise is to increase demand for it. This phenomenon is known as the Giffen paradox.

In economics, a necessity good or a necessary good is a type of normal good, and they are usually classified as an inferior good. Necessity goods are product(s) and services that consumers will buy regardless of the changes in their income levels, therefore making these products less sensitive to income change. Necessity goods are goods or services which are indispensable to humans, such as food, water, or shelter. Necessity goods often do not have close substitute goods.

As for any other normal good, an income rise will lead to a rise in demand, but the increase for a necessity good is less than proportional to the rise in income, so the proportion of expenditure on these goods falls as income rises. If income elasticity of demand is lower than unity, it is a necessity good. This observation for food, known as Engel's law, states that as income rises, the proportion of income spent on food falls, even if absolute expenditure on food rises. This makes the income elasticity of demand for food between zero and one.