Microeconomics: Why a Diamond Costs More Than Water, But You'd Die Without Water

Microeconomics is the study of how individuals, households, and firms make decisions and interact in markets. Core principles include scarcity (unlimited wants vs. limited resources), opportunity cost (next best alternative given up), marginal analysis (incremental changes, marginal benefit vs. marginal cost), and incentives (responses to prices, taxes, subsidies). Key players are households (consume, supply labor), firms (produce, demand labor), and government (rules, taxes, public goods). Demand & supply follow the law of demand (price up → quantity demanded down) and law of supply (price up → quantity supplied up), reaching equilibrium where quantity demanded equals quantity supplied; shortages or surpluses push price back. Elasticity includes price elasticity of demand (% change Qd / % change P: elastic >1 for luxury goods/many substitutes, inelastic <1 for necessities/few substitutes), income elasticity (normal goods positive, inferior goods negative), and cross-price elasticity (substitutes positive, complements negative). Market structures are perfect competition (many firms, identical products, price takers, no barriers, zero long-run profit), monopoly (one firm, unique product, price maker, high barriers, long-run profit), monopolistic competition (many firms, differentiated products, low barriers, zero long-run profit), and oligopoly (few firms, strategic interdependence/game theory, high barriers). Consumer & producer behavior involves utility maximization (consumers allocate income so marginal utility per dollar is equal across goods), profit maximization (firms produce where marginal revenue = marginal cost), and costs (fixed vs. variable, average vs. marginal, short-run vs. long-run). Market failures & government address externalities (costs/benefits to third parties: pollution → tax, education → subsidy), public goods (non-rival, non-excludable like national defense → free rider problem), information asymmetry (one party knows more, e.g., used cars, insurance), and government intervention (taxes, subsidies, price controls/ceilings/floors, regulation). Key graphs include demand & supply curves (shifts vs. movements), elasticity along a linear demand curve, consumer & producer surplus (deadweight loss from price controls/taxes), perfect competition (short-run profit, long-run equilibrium), monopoly (inefficiency, price > MC), and monopolistic competition (long-run tangency).