- Scarcity
- The basic economic problem: limited resources against unlimited wants, forcing every society to make choices.
- Opportunity cost
- The value of the next-best alternative given up when a choice is made.
- Marginal analysis
- Comparing the additional benefit and additional cost of one more unit of an activity; do it while MB ≥ MC.
- Marginal benefit
- The additional satisfaction or value from consuming one more unit of a good.
- Trade-off
- Giving up one thing to get another because resources are scarce.
- Production possibilities curve (PPC)
- A graph of the maximum combinations of two goods an economy can produce with resources fully and efficiently used.
- Point inside the PPC
- An inefficient combination — resources are unemployed or misused.
- Point outside the PPC
- An unattainable combination given current resources and technology.
- Why the PPC bows outward
- Because resources aren't equally suited to both goods, opportunity cost increases as you make more of one.
- Constant opportunity cost
- A straight-line PPC — resources are equally productive in both goods.
- Economic growth on the PPC
- An outward shift of the whole curve from more resources or better technology.
- Absolute advantage
- Producing more of a good than another producer with the same resources.
- Comparative advantage
- Producing a good at a lower opportunity cost than another producer.
- Who should specialize?
- The producer with the comparative advantage (lowest opportunity cost), not necessarily the absolute advantage.
- Gains from trade
- Both parties can consume beyond their own PPC when each specializes in its comparative advantage and trades.
- Terms of trade
- The rate at which two goods are exchanged; mutually beneficial when it lies between the two producers' opportunity costs.
- Factors of production
- The resources used to produce goods: land, labor, capital, and entrepreneurship.
- Microeconomics
- The study of individual decision-makers — consumers, firms, and specific markets.
- Macroeconomics
- The study of the economy as a whole: GDP, inflation, unemployment, and policy.
- Positive vs normative economics
- Positive describes what is (testable); normative prescribes what ought to be (value judgment).
- Rational self-interest
- The assumption that decision-makers weigh costs and benefits to make themselves as well off as possible.
- Normal good
- A good whose demand rises when income rises (positive income elasticity).
- Inferior good
- A good whose demand falls when income rises (negative income elasticity).
- Specialization
- Concentrating production on the goods one makes at lowest opportunity cost, then trading.
- Marginal product
- The additional output from adding one more unit of an input.
- Utility
- The satisfaction a consumer gets from a good or service.
- Sunk cost
- A cost already incurred that cannot be recovered; it should not affect marginal decisions.
- Capital (economics)
- Manufactured goods used to produce other goods, such as machines and tools.
- Allocative efficiency
- Producing the combination of goods most valued by society, where marginal benefit equals marginal cost.
- Law of demand
- As price rises, quantity demanded falls (and vice versa), all else equal — the demand curve slopes down.
- Law of supply
- As price rises, quantity supplied rises (and vice versa), all else equal — the supply curve slopes up.
- Change in quantity demanded
- A movement along a fixed demand curve caused by a change in the good's own price.
- Change in demand
- A shift of the whole demand curve caused by a non-price determinant.
- Determinants of demand
- Income, tastes, prices of related goods, expectations, and number of buyers.
- Determinants of supply
- Input prices, technology, prices of related goods, expectations, number of sellers, taxes and subsidies.
- Substitute goods
- Goods used in place of each other; a price rise in one raises demand for the other (positive cross-price elasticity).
- Complementary goods
- Goods used together; a price rise in one lowers demand for the other (negative cross-price elasticity).
- Equilibrium
- The price and quantity where quantity demanded equals quantity supplied and the market clears.
- Surplus (excess supply)
- When price is above equilibrium, quantity supplied exceeds quantity demanded; price falls.
- Shortage (excess demand)
- When price is below equilibrium, quantity demanded exceeds quantity supplied; price rises.
- Double shift
- When both curves shift, either equilibrium price or quantity is indeterminate (depends on relative shift sizes).
- Price elasticity of demand
- % change in quantity demanded ÷ % change in price; measures responsiveness to price.
- Elastic demand
- Elasticity greater than 1 in absolute value — quantity is very responsive to price.
- Inelastic demand
- Elasticity less than 1 in absolute value — quantity is not very responsive to price.
- Unit elastic demand
- Elasticity equal to 1; total revenue is at its maximum.
- Perfectly inelastic demand
- Elasticity = 0; a vertical demand curve (quantity doesn't change with price).
- Perfectly elastic demand
- Elasticity = infinity; a horizontal demand curve (any price change ends all sales).
- Determinants of elasticity
- Number of substitutes, necessity vs luxury, share of income, and time horizon.
- Elasticity and total revenue
- Elastic: a price cut raises total revenue. Inelastic: a price rise raises total revenue.
- Cross-price elasticity
- % change in demand for one good ÷ % change in price of another; positive = substitutes, negative = complements.
- Income elasticity of demand
- % change in demand ÷ % change in income; positive = normal good, negative = inferior good.
- Price elasticity of supply
- % change in quantity supplied ÷ % change in price; higher the more time producers have to adjust.
- Consumer surplus
- The difference between willingness to pay and price paid; the area below demand and above price.
- Producer surplus
- The difference between price received and the minimum sellers would accept; area above supply and below price.
- Total surplus
- Consumer surplus plus producer surplus; maximized at the free-market equilibrium.
- Deadweight loss
- The loss of total surplus when the market isn't at its efficient quantity.
- Price ceiling
- A legal maximum price; binding only if set below equilibrium, where it creates a shortage.
- Price floor
- A legal minimum price; binding only if set above equilibrium, where it creates a surplus.
- Binding price control
- A control that actually changes the market outcome (ceiling below, or floor above, equilibrium).
- Excise tax
- A per-unit tax on a good that shifts the supply curve up by the tax amount, raising price and lowering quantity.
- Tax incidence
- How the burden of a tax is split between buyers and sellers; the more inelastic side bears more of it.
- Subsidy
- A per-unit government payment that shifts supply down, lowering price and raising quantity.
- Marginal utility
- The additional satisfaction from consuming one more unit of a good.
- Law of diminishing marginal utility
- Each additional unit consumed gives less added satisfaction than the one before.
- Utility-maximizing rule
- Allocate spending so the marginal utility per dollar (MU ÷ P) is equal across all goods.
- Demand curve and marginal utility
- The demand curve slopes down partly because of diminishing marginal utility.
- Income effect
- As a good's price falls, your real purchasing power rises, so you can buy more.
- Substitution effect
- As a good's price falls, you switch toward it from now-relatively-pricier substitutes.
- Normal vs inferior on income change
- A rise in income increases demand for normal goods and decreases demand for inferior goods.
- Shift vs movement
- Own-price change = movement along the curve; any other determinant = shift of the curve.
- Quantity demanded
- The amount buyers are willing and able to buy at a specific price.
- Total revenue
- Price times quantity (TR = P × Q).
- Effect of a binding price ceiling
- A persistent shortage, possible black markets, and deadweight loss.
- Short run
- A period in which at least one input (usually capital) is fixed.
- Long run
- A period in which all inputs are variable and firms can enter or exit.
- Fixed cost
- A cost that does not change with output (e.g., rent); exists only in the short run.
- Variable cost
- A cost that changes with output (e.g., labor, materials).
- Total cost
- TC = total fixed cost + total variable cost.
- Average total cost (ATC)
- Total cost divided by quantity (TC ÷ Q); U-shaped in the short run.
- Average variable cost (AVC)
- Variable cost divided by quantity (TVC ÷ Q).
- Average fixed cost (AFC)
- Fixed cost divided by quantity (TFC ÷ Q); always falls as output rises.
- Marginal cost (MC)
- The added cost of producing one more unit: change in total cost ÷ change in quantity.
- MC and the average curves
- MC passes through the minimum of both ATC and AVC.
- Why MC eventually rises
- Diminishing marginal returns — added inputs add less output, so each unit costs more.
- Law of diminishing marginal returns
- As a variable input is added to fixed inputs, marginal product eventually declines.
- Total product
- The total output produced with a given amount of inputs.
- Marginal product
- The extra output from one more unit of a variable input.
- Average product
- Total product divided by the quantity of the variable input.
- Economies of scale
- Long-run average total cost falls as output rises (often from specialization).
- Diseconomies of scale
- Long-run average total cost rises as output rises (often from coordination problems).
- Constant returns to scale
- Long-run average total cost is flat as output rises.
- Profit maximization rule
- Produce the quantity where marginal revenue equals marginal cost (MR = MC).
- Marginal revenue (MR)
- The added revenue from selling one more unit.
- Accounting profit
- Total revenue minus explicit (out-of-pocket) costs.
- Economic profit
- Total revenue minus explicit AND implicit (opportunity) costs.
- Normal profit
- Zero economic profit — the firm earns just enough to keep resources in their current use.
- Implicit cost
- The opportunity cost of using resources the firm already owns.
- Perfect competition
- Many firms, identical products, free entry/exit, and perfect information; firms are price takers.
- Price taker
- A firm too small to affect market price; it faces a horizontal demand curve.
- Perfectly competitive firm's demand
- Horizontal at the market price, so P = MR = AR.
- PC firm's profit-max output
- Produce where P = MC (since P = MR for a price taker).
- Shutdown rule (short run)
- Shut down if price is below the minimum of average variable cost (P < AVC).
- Shutdown point
- The minimum point of the AVC curve.
- Break-even point
- The minimum point of the ATC curve, where economic profit is zero.
- Short-run profit for a PC firm
- Earned when P > ATC at the profit-maximizing quantity.
- Short-run loss for a PC firm
- Incurred when AVC < P < ATC; the firm keeps operating to cover some fixed costs.
- Long-run equilibrium in PC
- Free entry/exit drives economic profit to zero: P = MR = MC = minimum ATC.
- Productive efficiency
- Producing at the lowest possible cost (minimum ATC) — achieved by PC in the long run.
- Allocative efficiency in PC
- Achieved where P = MC, so the value of the last unit equals its cost.
- Entry effect on price
- New firms increase market supply, lowering price until profits disappear.
- Exit effect on price
- Firms leaving decrease market supply, raising price until losses disappear.
- Firm vs market supply
- Market supply is the horizontal sum of all firms' marginal cost curves above AVC.
- Explicit cost
- A direct, out-of-pocket payment for resources (wages, rent, materials).
- Why ATC is U-shaped
- Falling average fixed cost dominates at low output; rising marginal cost dominates at high output.
- Profit per unit
- Price minus average total cost (P − ATC) at the profit-maximizing quantity.
- MR for a price taker
- Equals the market price, because each extra unit sells at that same price.
- Imperfect competition
- Markets where firms have some market power and face a downward-sloping demand curve.
- Market power
- The ability of a firm to influence the price of its product.
- Monopoly
- A market with a single seller of a product with no close substitutes and high barriers to entry.
- Barriers to entry
- Obstacles like economies of scale, patents, control of a resource, or legal restrictions that block new firms.
- Price maker
- A firm that sets its price by choosing output along a downward-sloping demand curve.
- MR below price for a monopoly
- Because it must lower price on all units to sell more, marginal revenue is below price.
- Monopoly output and price
- Produce where MR = MC, then charge the higher price on the demand curve.
- Monopoly inefficiency
- Output is restricted and price exceeds marginal cost, causing deadweight loss.
- Natural monopoly
- An industry where one firm can supply the whole market at lower cost due to large economies of scale.
- Price discrimination
- Charging different buyers different prices for the same good based on willingness to pay.
- Conditions for price discrimination
- Market power, ability to separate buyers, and prevention of resale.
- Perfect price discrimination
- Charging each buyer their maximum willingness to pay; captures all surplus, no deadweight loss.
- Monopolistic competition
- Many firms selling differentiated products with free entry and some pricing power.
- Product differentiation
- Making a product distinct (brand, quality, location) to gain some market power.
- Monopolistic competition long run
- Entry drives economic profit to zero; firms produce with excess capacity.
- Excess capacity
- Producing below the minimum-ATC output, so the firm isn't productively efficient.
- Oligopoly
- A market dominated by a few interdependent firms.
- Interdependence
- Each oligopolist's best choice depends on what rivals are expected to do.
- Game theory
- The study of strategic decisions among interdependent players.
- Payoff matrix
- A table showing each player's outcomes for every combination of strategies.
- Dominant strategy
- A strategy that is best for a player regardless of what the other does.
- Nash equilibrium
- An outcome where no player can do better by changing strategy alone.
- Prisoner's dilemma
- A game where individually rational choices lead to a jointly worse outcome.
- Collusion
- Firms cooperating to set price or output like a monopoly; often illegal and unstable.
- Cartel
- A group of firms that collude to act as a single monopolist (e.g., OPEC).
- Why cartels break down
- Each member has an incentive to cheat by producing more, undermining the agreement.
- Monopoly demand vs MR
- The demand (average revenue) curve lies above the marginal revenue curve.
- Allocative inefficiency of market power
- Price exceeds marginal cost, so society would gain from more output that isn't produced.
- Antitrust laws
- Laws that limit market power and prohibit anti-competitive practices like collusion.
- Single-price monopoly profit
- Earned where P > ATC at the quantity where MR = MC.
- Patents and monopoly
- Government grants of temporary exclusive rights that create legal barriers to entry.
- Kinked demand curve
- A model of oligopoly pricing where rivals match price cuts but not price increases.
- Comparing structures
- From most to least competitive: perfect competition, monopolistic competition, oligopoly, monopoly.
- Deregulation of a monopoly
- Removing legal barriers to allow competition and lower prices.
- Factor market
- A market where firms buy resources (labor, land, capital) and households sell them.
- Derived demand
- Demand for an input that comes from demand for the product it helps produce.
- Marginal revenue product (MRP)
- The extra revenue from hiring one more unit of a resource: marginal product × marginal revenue.
- MRP as factor demand
- A firm's MRP curve is its demand curve for that input.
- Marginal resource cost (MRC)
- The additional cost of hiring one more unit of a resource.
- Hiring rule
- Hire each unit of a factor up to where MRP equals MRC.
- MRP = MRC vs MR = MC
- The factor-market hiring rule is the twin of the product-market output rule.
- Competitive labor market wage
- Set where market labor supply meets market labor demand; each firm is a wage taker.
- Firm's hiring in a competitive labor market
- Hire workers up to where MRP equals the market wage.
- Shifts in labor demand
- Caused by changes in product price, productivity, or the prices of other inputs.
- Shifts in labor supply
- Caused by changes in population, preferences, wages in other jobs, or immigration.
- Monopsony
- A market with a single buyer of a resource, often labor.
- Monopsony outcome
- Hires fewer workers and pays a lower wage than a competitive labor market.
- MRC under monopsony
- Rises faster than the wage, because hiring one more worker raises the wage for all workers.
- Marginal product of labor
- The extra output produced by one more worker.
- Why labor demand slopes down
- Diminishing marginal product lowers MRP as more workers are hired.
- Least-cost rule
- Hire inputs so the marginal product per dollar (MP ÷ P) is equal across all inputs.
- Profit-maximizing input rule
- Employ each input until its MRP equals its price (MRP = MRC for every input).
- Economic rent
- Payment to a factor above the minimum needed to keep it in its current use.
- Determinants of wage differences
- Productivity, human capital, working conditions, and skill scarcity.
- Human capital
- The knowledge and skills workers gain through education and experience that raise productivity.
- Capital market
- Where firms acquire physical or financial capital; demand depends on the return relative to cost.
- Labor as a derived demand
- Firms hire workers not for their own sake but to produce salable output.
- Effect of higher product price on labor demand
- Raises MRP, shifting the firm's labor demand curve right.
- Wage taker
- A firm in a competitive labor market that must pay the going market wage.
- Market failure
- When a free market fails to allocate resources efficiently on its own.
- Externality
- A cost or benefit imposed on third parties not part of a transaction.
- Negative externality
- A cost on third parties (e.g., pollution); the market overproduces.
- Positive externality
- A benefit to third parties (e.g., vaccination); the market underproduces.
- Marginal social cost (MSC)
- Marginal private cost plus any external cost; relevant for negative externalities.
- Marginal social benefit (MSB)
- Marginal private benefit plus any external benefit; relevant for positive externalities.
- Efficient quantity
- Where marginal social benefit equals marginal social cost (MSB = MSC).
- Pigouvian tax
- A per-unit tax equal to the external cost that corrects a negative externality.
- Corrective subsidy
- A per-unit subsidy equal to the external benefit that corrects a positive externality.
- Coase theorem
- If property rights are clear and bargaining is costless, private parties can solve externalities themselves.
- Public good
- A good that is non-excludable and non-rival, like national defense.
- Non-excludable
- You cannot prevent non-payers from using the good.
- Non-rival
- One person's use does not reduce the amount available to others.
- Free-rider problem
- People enjoy a good without paying, so markets underprovide public goods.
- Private good
- A good that is both excludable and rival in consumption.
- Common resource
- A good that is non-excludable but rival, prone to overuse.
- Tragedy of the commons
- The overuse and depletion of a common resource because no one bears its full cost.
- Lorenz curve
- A graph showing the cumulative share of income earned by cumulative shares of the population.
- Gini coefficient
- A 0-to-1 measure of income inequality; 0 is perfect equality, 1 is maximum inequality.
- Progressive tax
- A tax that takes a larger percentage of income as income rises.
- Regressive tax
- A tax that takes a larger percentage of income from low earners than high earners.
- Proportional tax
- A tax that takes the same percentage of income at all income levels (flat tax).
- Transfer payment
- A government payment (like welfare) for which no good or service is exchanged.
- Antitrust regulation
- Government action to limit monopoly power and promote competition.
- Why monopoly is a market failure
- Restricted output and price above marginal cost create deadweight loss.