Introduction
Microeconomics is the branch of economics that studies how individuals, households, workers, and businesses make choices and how those choices interact in particular markets.
Instead of examining the entire economy, microeconomics asks questions such as: Why does the price of a product rise? How does a consumer decide what to buy? How much should a company produce? What happens when a government sets a minimum price? Why do monopolies behave differently from competitive firms?
Microeconomics is built around several connected ideas: scarcity, opportunity cost, incentives, supply and demand, elasticity, consumer choice, production costs, competition, and market failure. These concepts help explain everyday decisions involving food, housing, wages, transportation, business strategy, taxes, and environmental policy.
Learning Objectives
After studying this guide, you should be able to:
Explain scarcity, opportunity cost, marginal analysis, and incentives.
Understand supply, demand, equilibrium, shortages, and surpluses.
Calculate and interpret basic elasticity measures.
Explain consumer choice, utility, and budget constraints.
Distinguish fixed, variable, average, and marginal costs.
Compare perfect competition, monopoly, monopolistic competition, and oligopoly.
Explain externalities, public goods, taxes, subsidies, price controls, and other market interventions.
Microeconomics vs Macroeconomics
The two main branches of economics focus on different levels of analysis.
Microeconomics
Microeconomics examines:
Individual consumers
Workers
Firms
Product prices
Specific industries
Individual markets
Examples include the market for coffee, apartment rents, mobile phones, or labor in the construction industry.
Macroeconomics
Macroeconomics examines economy-wide outcomes such as:
GDP
Inflation
Unemployment
Economic growth
National interest rates
Memory Tip
Micro → individual markets
Macro → whole economy
Scarcity and Choice
Scarcity means resources are limited relative to the number of possible uses for them.
Scarce resources include:
Time
Money
Labor
Land
Raw materials
Machinery
Because resources are scarce, every economic decision involves a choice.
A household deciding between saving money and taking a vacation faces scarcity. A business choosing whether to build a new factory faces the same basic problem.
Opportunity Cost
The opportunity cost of a decision is the value of the next-best alternative given up.
Suppose a student spends three hours studying economics instead of working for $15 per hour.
The lost $45 of earnings forms part of the opportunity cost of studying.
Opportunity cost can involve:
Money
Time
Leisure
Production
Alternative investments
Memory Tip
Opportunity cost = best alternative sacrificed
Marginal Analysis
Economists often study decisions at the margin.
Marginal means the effect of one additional unit.
Important terms include:
Marginal cost
Marginal benefit
Marginal revenue
Marginal utility
A decision-maker may continue an activity while the additional benefit exceeds the additional cost.
This can be summarized as:
Continue while Marginal Benefit ≥ Marginal Cost
Incentives
An incentive changes the costs or benefits associated with an action.
Examples include:
A discount encouraging purchases.
A tax discouraging consumption.
A higher wage encouraging additional work.
A subsidy encouraging production.
Microeconomics studies how people respond when incentives change.
Demand
Demand describes how much of a product consumers are willing and able to purchase at different prices.
The IMF explains that under ordinary conditions, quantity demanded tends to fall as price rises, other things remaining equal. (imf.org)
Law of Demand
Other things equal:
Price rises → Quantity demanded falls
Price falls → Quantity demanded rises
This relationship is represented by a downward-sloping demand curve in the standard model.
What Shifts Demand?
Demand can shift because of changes in:
Consumer income
Population
Tastes and preferences
Expectations
Prices of related goods
A demand shift is different from movement along a demand curve.
Movement Along Demand vs Demand Shift
This is a common quiz distinction.
Movement Along the Demand Curve
Caused by a change in the product's own price.
Shift of the Demand Curve
Caused by another factor.
Example:
If coffee becomes cheaper, there is movement along the demand curve for coffee.
If tea becomes more expensive and people switch to coffee, the entire demand curve for coffee may shift outward.
Substitute and Complementary Goods
Substitutes
Substitutes are goods consumers may use in place of one another.
Examples:
Tea and coffee
Bus travel and train travel
If the price of tea rises, demand for coffee may increase.
Complements
Complements are goods often consumed together.
Examples:
Cars and fuel
Printers and ink
If the price of one complement rises sharply, demand for the other may fall.
Normal and Inferior Goods
Normal Good
Demand for a normal good generally increases when consumer income rises.
Inferior Good
Demand for an inferior good may decrease as income rises because consumers switch to preferred alternatives.
The term inferior does not mean poor quality. It describes how demand responds to income.
Supply
Supply describes how much producers are willing and able to sell at different prices.
Under ordinary conditions:
Price rises → Quantity supplied rises
Price falls → Quantity supplied falls
The IMF describes supply and demand as central mechanisms determining prices and quantities in markets. (imf.org)
What Shifts Supply?
Supply can change because of:
Input prices
Technology
Taxes
Subsidies
Number of sellers
Weather
Expectations
Example:
If electricity becomes cheaper for manufacturers, production costs may fall and supply may increase.
Market Equilibrium
Market equilibrium occurs where quantity demanded equals quantity supplied.
At equilibrium:
Qd = Qs
The corresponding price is the equilibrium price.
Shortage
A shortage occurs when:
Quantity demanded > Quantity supplied
This may place upward pressure on price.
Surplus
A surplus occurs when:
Quantity supplied > Quantity demanded
This may place downward pressure on price.
Elasticity
Elasticity measures responsiveness.
Price Elasticity of Demand
Price elasticity of demand measures how strongly quantity demanded responds to a price change.
A basic formula is:
Price Elasticity of Demand = % Change in Quantity Demanded ÷ % Change in Price
Elastic Demand
Demand is relatively elastic when consumers respond strongly to a price change.
Products tend to be more elastic when:
Many substitutes exist.
The purchase can be delayed.
The product takes a large share of income.
Inelastic Demand
Demand is relatively inelastic when quantity changes relatively little after a price change.
Demand may be more inelastic when:
Few substitutes exist.
The product is considered necessary.
Consumers have little time to adjust.
Memory Tip
Elastic → strong response
Inelastic → weak response
Other Elasticities
Income Elasticity of Demand
Measures how demand changes when income changes.
Cross-Price Elasticity
Measures how demand for one good responds to the price of another.
Positive cross-price elasticity often suggests substitutes.
Negative cross-price elasticity often suggests complements.
Price Elasticity of Supply
Measures how strongly quantity supplied responds to price.
Supply usually becomes more elastic when producers have more time to adjust production.
Consumer Choice
Consumers face limited income and must choose among competing products.
Microeconomics often represents this using:
Preferences
Utility
Prices
Budget constraints
Utility
Utility represents satisfaction or benefit obtained from consuming goods or services.
Utility is an analytical concept. Economists do not need to assume that satisfaction can always be measured precisely in real life.
Marginal Utility
Marginal utility is the additional satisfaction from consuming one more unit.
Diminishing Marginal Utility
The principle of diminishing marginal utility suggests that, in many situations, the additional satisfaction gained from each extra unit decreases.
Example:
The first slice of pizza may provide substantial satisfaction.
The fifth consecutive slice may provide much less.
Budget Constraint
A budget constraint shows the combinations of goods and services a consumer can afford given:
Income
Prices
If income rises, the consumer can generally afford more combinations.
If the price of a product rises, the affordable set changes.
Consumer choice theory examines how people choose among these possibilities.
Consumer Surplus
Consumer surplus is the difference between:
What a consumer is willing to pay
What the consumer actually pays
Example:
If someone is willing to pay $50 for a book but purchases it for $35:
Consumer surplus = $15
Producer Surplus
Producer surplus is closely related to the difference between the price producers receive and the minimum amount required to make supplying units worthwhile.
Consumer and producer surplus are commonly used to analyze gains from market exchange.
Production
Businesses combine inputs to produce goods and services.
Inputs may include:
Labor
Machinery
Buildings
Raw materials
Energy
A production function describes the relationship between inputs and output.
Fixed and Variable Costs
Fixed Costs
Fixed costs do not change with current production quantity in the short run.
Examples may include:
Rent
Some insurance payments
Certain equipment costs
A business may have to pay them even when output is zero.
Variable Costs
Variable costs change as output changes.
Examples include:
Raw materials
Production energy
Hourly labor in some settings
Total and Average Cost
Total Cost = Fixed Cost + Variable Cost
Average total cost is:
Average Total Cost = Total Cost ÷ Quantity Produced
Average cost tells us the cost per unit.
Marginal Cost
Marginal cost is the additional cost of producing one more unit.
A simplified formula is:
Marginal Cost = Change in Total Cost ÷ Change in Quantity
Marginal cost is extremely important because businesses often make production decisions based on the cost of additional output rather than average cost alone.
Diminishing Marginal Returns
In the short run, at least one input may be fixed.
If a business keeps adding workers to a fixed amount of machinery or workspace, additional output may eventually increase more slowly.
This principle is called diminishing marginal returns.
It does not mean total output must immediately fall.
It means the extra output produced by each additional variable input eventually declines.
Revenue and Profit
Total Revenue
Total Revenue = Price × Quantity Sold
Profit
Profit = Total Revenue − Total Cost
However, economists distinguish accounting profit from economic profit.
Accounting vs Economic Profit
Accounting Profit
Accounting profit subtracts explicit monetary costs such as:
Wages
Rent
Materials
Economic Profit
Economic profit also subtracts opportunity costs.
Suppose a business owner could earn $60,000 working elsewhere.
That forgone salary is an economic opportunity cost of running the business.
Common Quiz Trap
A firm may earn positive accounting profit but zero or negative economic profit.
Market Structures
Microeconomics classifies markets according to factors such as:
Number of sellers
Product differentiation
Barriers to entry
Control over price
Four common models are:
Perfect competition
Monopolistic competition
Oligopoly
Monopoly
Perfect Competition
A perfectly competitive market model assumes:
Many buyers and sellers
Identical products
Easy entry and exit
Strong information
No individual firm can control market price
Individual firms are therefore described as price takers.
Perfect competition is mainly a benchmark model rather than a perfect description of most real markets.
Monopoly
A monopoly exists when one seller controls the supply of a product without close competition.
Monopolies may emerge because of:
Legal protection
Control over key resources
Network effects
Economies of scale
High barriers to entry
A monopoly generally has more power over price than a perfectly competitive firm.
Competition authorities examine monopolization and anticompetitive practices because weak competition can reduce consumer choice and raise prices. (ftc.gov)
Monopolistic Competition
Monopolistic competition combines:
Many firms
Differentiated products
Relatively easy entry
Examples may include:
Restaurants
Clothing brands
Cafés
Hair salons
Businesses compete through:
Price
Quality
Branding
Location
Oligopoly
An oligopoly contains a small number of major firms.
Because there are few large competitors, each firm's decisions may affect the others.
Oligopolistic firms may pay close attention to:
Prices
Advertising
Product launches
Capacity decisions
Game theory is often used to study this strategic interaction.
Game Theory
Game theory studies situations where one person's or firm's best choice depends on what others do.
An important example is the prisoner's dilemma, which illustrates why individually rational choices can sometimes produce a worse collective outcome.
Game theory is especially useful for analyzing:
Oligopoly
Bargaining
Auctions
Strategic competition
Barriers to Entry
A barrier to entry makes it difficult for new firms to enter a market.
Examples include:
Very high startup costs
Patents
Government licenses
Control of essential infrastructure
Strong network effects
High barriers can reduce competitive pressure.
Economies of Scale
Economies of scale occur when average cost falls as production expands.
Possible causes include:
Specialized machinery
Bulk purchasing
Division of labor
Spreading fixed costs over more units
When economies of scale are extremely strong, one large producer may sometimes produce at lower cost than many small producers.
Price Discrimination
Price discrimination occurs when a seller charges different prices to different customers or groups for reasons not fully explained by differences in production cost.
Examples can include:
Student discounts
Airline fares
Peak and off-peak pricing
Successful price discrimination usually requires the seller to have some market power and the ability to prevent easy resale.
Market Failure
A market failure occurs when an unregulated market does not allocate resources efficiently under the relevant economic model.
Important sources include:
Externalities
Public goods
Market power
Information problems
Market failure does not automatically mean that any government intervention will improve the outcome. Policy itself can also involve costs and imperfect information.
Externalities
An externality occurs when an activity affects someone who is not directly part of the transaction.
Negative Externality
A factory produces goods but also creates pollution affecting nearby residents.
The market price may not fully reflect the external damage.
Positive Externality
Vaccination can benefit the vaccinated individual while also reducing disease transmission to others.
Education can similarly generate benefits beyond the individual student.
Public Goods
A public good has two classic features:
Non-Rival
One person's use does not significantly reduce another person's ability to benefit.
Non-Excludable
It is difficult to prevent non-payers from benefiting.
A common example is national defense.
Public goods can create a free-rider problem, where people receive benefits without directly paying, making private provision more difficult.
Common Resources
A common resource is generally:
Rival in consumption
Difficult to exclude users from
Examples can include:
Ocean fisheries
Shared grazing land
Excessive use can create the tragedy of the commons, where individual incentives contribute to overuse of a shared resource.
Information Asymmetry
Information asymmetry occurs when one side of a transaction has more relevant information than the other.
Examples include:
A used-car seller knowing more about the vehicle than the buyer.
An insurance customer knowing more about personal risk than the insurer.
Two important concepts are:
Adverse Selection
Problems that occur before a transaction because hidden information affects who participates.
Moral Hazard
Problems that occur after an agreement because behavior changes when someone is protected from some consequences.
Government Intervention
Governments may intervene in markets through:
Taxes
Subsidies
Price ceilings
Price floors
Regulation
Competition policy
Public provision
The effect depends on how the policy changes incentives.
Taxes
A tax can increase the gap between the price buyers pay and the price sellers receive.
Taxes can:
Reduce the quantity traded
Generate government revenue
Change consumer and producer behavior
Tax Incidence
Tax incidence concerns who actually bears the economic burden of a tax.
The side of the market that is less responsive to price—more inelastic—typically bears more of the burden.
This is different from who legally sends the tax payment to the government.
Subsidies
A subsidy reduces costs or provides financial support.
Governments may subsidize:
Education
Agriculture
Energy
Research
Public transportation
A subsidy can increase production or consumption but also requires financing.
Price Ceiling
A price ceiling sets a legal maximum price.
If set below market equilibrium, it can create:
Quantity demanded > Quantity supplied
which means a shortage may develop.
Rent controls are a commonly discussed example.
Price Floor
A price floor sets a legal minimum price.
If set above equilibrium:
Quantity supplied > Quantity demanded
which can create a surplus.
Minimum-wage analysis uses similar supply-and-demand logic in labor markets, although real labor markets can be more complex than the simplest competitive model.
Deadweight Loss
A deadweight loss represents gains from trade that disappear because mutually beneficial transactions no longer occur.
Taxes, monopoly pricing, and certain other distortions can create deadweight loss in standard economic models.
It represents lost total surplus rather than a transfer from one group to another.
Factor Markets
Microeconomics also studies markets for productive resources.
These include markets for:
Labor
Capital
Land
Businesses demand these inputs because they help produce goods and services.
Labor Demand
A firm's demand for workers depends partly on the value of what workers can produce.
An additional worker is more valuable when:
Worker productivity is high.
The product sells at a high price.
This creates what economists call derived demand: demand for labor comes from demand for the output workers produce.
Positive vs Normative Economics
Positive Economics
Positive economics examines factual or testable statements.
Example:
A higher tax increases the price paid by consumers under these assumptions.
Normative Economics
Normative economics involves judgments about what should happen.
Example:
The government should raise this tax.
Memory Tip
Positive → what is
Normative → what ought to be
Common Microeconomics Mistakes
Demand and Quantity Demanded Are Different
Demand refers to the entire relationship.
Quantity demanded is one amount at one particular price.
A Price Change Does Not Shift the Same Product's Demand Curve
It normally causes movement along the curve.
Scarcity Does Not Mean Something Is Rare
Even common resources are scarce if they cannot satisfy every possible use.
Profit Is Not the Same as Revenue
Revenue → money received from sales
Profit → revenue minus cost
Fixed Cost Does Not Mean the Cost Never Changes Forever
It means the cost does not change with output within the relevant short-run analysis.
Monopoly Does Not Simply Mean a Large Company
A monopoly concerns market structure and lack of close competition, not company size alone.
Externality Does Not Mean Any Side Effect
It specifically involves effects on people outside the direct transaction that are not fully reflected in market prices.
Memory Tips
For market curves:
Demand → buyers
Supply → sellers
Price change → movement
Other factor → shift
For elasticity:
Elastic → responsive
Inelastic → less responsive
For costs:
FC → fixed
VC → varies
MC → next unit
For markets:
Perfect competition → many identical sellers
Monopolistic competition → many differentiated sellers
Oligopoly → few major firms
Monopoly → one seller
For market failure:
Externality → third-party effect
Public good → non-rival + non-excludable
Asymmetric information → unequal knowledge
Summary
Microeconomics studies how individual consumers, workers, and businesses make choices and interact within markets.
Supply and demand explain how prices and quantities are determined in many markets. Elasticity measures how strongly buyers and sellers respond when economic conditions change.
Consumers choose among products subject to prices, preferences, and budget constraints. Firms make production decisions by comparing revenues and costs, especially marginal revenue and marginal cost.
Different market structures produce different competitive conditions. Perfect competition contains many price-taking firms, monopoly involves a single dominant seller, monopolistic competition features differentiated products, and oligopoly involves strategic interaction among a small number of large firms.
Markets can also fail to account for externalities, public goods, market power, or information problems. Governments may respond with taxes, subsidies, regulations, price controls, or competition policy, although these policies can also involve trade-offs.
For quiz preparation, the most important distinctions are demand vs quantity demanded, movement vs shift, fixed vs variable cost, accounting vs economic profit, elastic vs inelastic demand, and monopoly vs oligopoly.
FAQ
What is microeconomics?
Microeconomics studies decisions made by individuals, households, workers, businesses, and participants in particular markets.
What is opportunity cost?
Opportunity cost is the value of the best alternative sacrificed when a decision is made.
What happens when demand rises?
If supply remains unchanged, higher demand usually creates upward pressure on equilibrium price and increases equilibrium quantity.
What is elasticity?
Elasticity measures how strongly one economic variable responds to a change in another.
What is marginal cost?
Marginal cost is the additional cost of producing one additional unit of output.
What is the difference between revenue and profit?
Revenue is income received from sales. Profit is revenue minus costs.
What is a monopoly?
A monopoly is a market structure in which one seller controls the market without close competition.
What is an externality?
An externality is a cost or benefit affecting someone outside the direct market transaction.
What is a public good?
A public good is normally defined as both non-rival and non-excludable.
What is the difference between a price ceiling and a price floor?
A price ceiling establishes a maximum legal price. A price floor establishes a minimum legal price.
Key Takeaways
Microeconomics studies individual economic decisions and interactions within specific markets.
Supply and demand determine equilibrium prices and quantities in standard market models.
Elasticity measures how strongly consumers and producers respond to price, income, or other changes.
Firms compare costs, revenues, and marginal conditions when deciding how much to produce.
Externalities, public goods, market power, and information problems can prevent markets from reaching efficient outcomes.
References
International Monetary Fund — Supply and Demand: Why Markets Tick Beginner-friendly explanation of demand, supply, equilibrium, elasticity, shortages, surpluses, and market competition.
IMF — Supply and Demand: Why Markets TickU.S. Federal Trade Commission — Guide to Antitrust Laws Official overview of competition, monopolization, mergers, price fixing, and other practices relevant to market structure.
FTC — Guide to Antitrust LawsU.S. Department of Justice — Antitrust Laws and You Government guidance explaining competition law and why competitive markets matter to consumers and businesses.
U.S. Department of Justice — Antitrust Laws and YouOECD — Competition International policy resources covering competition, market power, entry barriers, regulation, and competition enforcement.
OECD — CompetitionU.S. Environmental Protection Agency — Economics and Environmental Policy Government resources showing how economic tools, incentives, costs, and benefits are used when analyzing environmental externalities and regulation.
EPA — Environmental EconomicsCongressional Budget Office — The Effects of Federal Policies on Labor Markets U.S. government economic analysis illustrating how taxes, benefits, wages, and other policies can affect labor supply and incentives.
CBO — Labor Market AnalysisWorld Bank — Competition Policy International development resources on competition, market efficiency, productivity, firm entry, and the effects of market power.
World Bank — Competition Policy