States that, all else being equal, as the price of a good or service increases, the quantity demanded will decrease, and vice versa. It describes an inverse relationship between price and quantity demanded.
This law explains why consumers generally buy less of something when its price rises.
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Equilibrium Price
Answer
The price at which the quantity demanded by consumers exactly equals the quantity supplied by producers, resulting in no surplus or shortage in the market. It is where the supply and demand curves intersect.
At this price, the market is 'cleared,' meaning all willing buyers and sellers can transact.
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Price Floor
Answer
A government-imposed minimum price that can be charged for a good or service, set above the equilibrium price, leading to a surplus. It prevents prices from falling below a certain level.
A common mistake is confusing it with a price ceiling; remember a 'floor' is a minimum, and if effective, it must be above the equilibrium to have an impact.
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Shift in Demand
Answer
A change in the quantity demanded at every possible price, caused by a change in a non-price determinant such as income, tastes, expectations, or the prices of related goods, represented by a movement of the entire demand curve.
This is distinct from a 'change in quantity demanded,' which is only a movement along the demand curve due to a price change.
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Price Elasticity of Demand (PED)
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A measure of the responsiveness of the quantity demanded of a good or service to a change in its price, calculated as the percentage change in quantity demanded divided by the percentage change in price. It indicates how sensitive consumers are to price changes.
Knowing PED helps businesses predict how a price change will affect their total revenue; elastic demand means total revenue moves inversely with price.
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Inelastic Demand
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Occurs when the percentage change in quantity demanded is less than the percentage change in price, meaning consumers are not very responsive to price changes (PED < 1). Necessities often have inelastic demand.
If demand is inelastic, a firm can increase total revenue by raising prices, as the quantity lost is proportionally smaller than the price gain.
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Cross-Price Elasticity of Demand (CPED)
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A measure of how the quantity demanded of one good responds to a change in the price of another good, indicating whether the goods are substitutes (positive CPED) or complements (negative CPED).
If CPED is positive, the goods are substitutes (e.g., Coke and Pepsi); if negative, they are complements (e.g., coffee and sugar).
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Utility
Answer
The satisfaction or benefit a consumer derives from consuming a good or service, which is subjective and not directly measurable but helps explain consumer choices. It represents the value an individual places on a good.
While not quantifiable in absolute terms, utility helps economists model how consumers make choices to maximize their satisfaction.
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Diminishing Marginal Utility
Answer
The principle that as a consumer consumes more units of a good or service, the additional satisfaction (marginal utility) gained from each successive unit consumed tends to decrease.
This explains why you might enjoy your first slice of pizza immensely, but the tenth slice provides very little additional satisfaction.
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Budget Constraint
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The limit on the consumption bundles that a consumer can afford, given their income and the prices of goods and services. It represents all possible combinations of goods a consumer can buy.
This line shows the trade-offs consumers face, highlighting that choices are limited by financial resources.
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Indifference Curve
Answer
A curve that shows all combinations of two goods that provide a consumer with the same level of total utility or satisfaction, meaning the consumer is indifferent between any points on the curve.
Higher indifference curves represent higher levels of utility, but they never intersect.
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Consumer Equilibrium
Answer
The point at which a consumer maximizes their total utility given their budget constraint, occurring where the highest attainable indifference curve is tangent to the budget line. At this point, the marginal utility per dollar spent is equal for all goods.
This is the optimal consumption bundle for a rational consumer, balancing satisfaction with affordability.
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Perfect Competition
Answer
A market structure characterized by many small firms, identical products, free entry and exit, and perfect information, resulting in firms being price takers with no market power.
It serves as a theoretical benchmark for maximum efficiency, though rarely seen in its pure form.
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Monopoly
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A market structure where a single firm is the sole producer of a good or service with no close substitutes, giving it significant market power and the ability to set prices.
Monopolies often arise due to high barriers to entry, such as patents or control of essential resources.
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Oligopoly
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A market structure characterized by a few large firms that dominate the market, producing either identical or differentiated products, and whose decisions are interdependent.
The interdependence among firms leads to strategic behavior, often analyzed using game theory.
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Barrier to Entry
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Any obstacle that makes it difficult or impossible for new firms to enter a market, such as high start-up costs, patents, government regulations, or control of essential resources.
Barriers to entry are crucial in determining the level of competition and profitability within a market.
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Fixed Cost
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Costs of production that do not vary with the quantity of output produced in the short run, such as rent for a factory or the cost of machinery.
Even if a firm produces zero output, it still incurs its fixed costs.
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Variable Cost
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Costs of production that change with the quantity of output produced, such as raw materials, wages for production workers, or electricity for operating machinery.
These costs are zero if no output is produced and increase as production rises.
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Marginal Cost (MC)
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The additional cost incurred by producing one more unit of a good or service, calculated as the change in total cost divided by the change in quantity.
Firms use marginal cost to decide whether to produce an additional unit; if marginal revenue exceeds marginal cost, producing more is profitable.
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Average Total Cost (ATC)
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The total cost of production divided by the total quantity of output produced, representing the cost per unit of output.
ATC helps firms determine their profitability at different production levels; if price is above ATC, the firm is making a profit.
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Economies of Scale
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The situation where a firm's average total cost of production decreases as its quantity of output increases, often due to specialization, bulk purchasing, or more efficient use of capital.
This concept explains why larger firms can sometimes produce goods at a lower cost per unit than smaller firms.
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Diseconomies of Scale
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The situation where a firm's average total cost of production increases as its quantity of output increases, often due to coordination problems, bureaucracy, or communication challenges in very large organizations.
Beyond a certain point, a firm can become too large and inefficient, leading to rising per-unit costs.
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Opportunity Cost
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The value of the next best alternative that must be foregone when a choice is made, representing the true cost of any decision.
Every economic decision involves an opportunity cost; choosing to study for an exam means forgoing time spent on a hobby.
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Market Failure
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A situation in which the free market mechanism, left to itself, fails to allocate resources efficiently, leading to a suboptimal outcome for society.
This provides a justification for potential government intervention in the economy.
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Externality
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A cost or benefit imposed on a third party who is not directly involved in the production or consumption of a good or service, leading to a divergence between private and social costs or benefits.
Pollution from a factory (negative externality) or the benefits of vaccination (positive externality) are classic examples.
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Public Good
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A good that is both non-rivalrous (one person's consumption does not diminish another's) and non-excludable (it is difficult to prevent people from consuming it even if they don't pay).
Due to the free-rider problem, public goods are typically underprovided by private markets and often require government provision, like national defense.
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Asymmetric Information
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A situation where one party in an economic transaction has more or better information than the other party, leading to inefficient outcomes.
This imbalance can lead to problems like adverse selection and moral hazard.
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Moral Hazard
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Occurs when one party in a transaction changes their behavior after the transaction has occurred, knowing that the other party bears the costs of that behavior.
An example is a person becoming less careful with their car after purchasing comprehensive insurance.
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Adverse Selection
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Occurs when one party in a transaction has better information about a hidden characteristic than the other party, leading to a selection of undesirable outcomes.
In health insurance, sicker people are more likely to purchase insurance, driving up costs for everyone.