Public Economics

Overview

Use a single framework for every topic in this unit. First, name the failure or goal: is it an externality, a public good, monopoly, missing information, macroeconomic instability or inequality? Second, list the feasible instruments: do nothing, regulate, tax or subsidise, provide publicly, or transfer income. Third, evaluate each instrument on efficiency, equity, revenue and feasibility, including the government failures that intervention can create. Fourth, state the incidence: the legal payer of a tax is not necessarily the economic bearer, and the intended beneficiary of a subsidy is not necessarily the actual beneficiary. Answers that follow that sequence are hard to fault, because they show the reasoning rather than merely asserting a conclusion.

Market failure and public goods

Market failure means the market outcome is not Pareto efficient. Externalities are the classic case: a production or consumption decision affects third parties without compensation through prices. A negative production externality, such as pollution, means social marginal cost exceeds private marginal cost, so the market produces too much; a Pigouvian tax equal to marginal external damage at the optimum restores efficiency by internalising the cost. A positive externality, such as vaccination or basic research, means social marginal benefit exceeds private benefit, so the market produces too little; a Pigouvian subsidy equal to marginal external benefit corrects it. The Coase insight is that with well-defined property rights and low transaction costs, private bargaining can reach efficiency regardless of who holds the rights, though the distribution of gains depends on the initial assignment; with high transaction costs or many parties, bargaining fails and policy is needed.

Public goods are non-excludable, meaning non-payers cannot be prevented from consuming, and non-rival, meaning one person consumption does not reduce availability for others. National defence and lighthouses are textbook examples, while many real goods are mixed: a road is non-rival until congested, and a broadcast can be made excludable by encryption. Non-excludability creates free riding: each person prefers others to pay, so private provision under-supplies the good and the market may provide none at all. The efficiency condition for a public good, the Samuelson condition, is that the sum of marginal rates of substitution across all consumers equals marginal cost, because all consumers enjoy the same unit simultaneously, unlike private goods where each consumer marginal rate equals price separately. Common pool resources are non-excludable but rival, such as fisheries and groundwater, and suffer overuse, the tragedy of the commons, unless access is regulated or property rights are defined. Merit goods, such as education and health care, are a distinct argument based on distributional values or consumer ignorance rather than pure efficiency, and they justify intervention even when markets are efficient in the narrow sense.

Regulation of markets

Regulation is the attempt to fix market outcomes without the government itself producing the good. For a natural monopoly, where average costs fall over the relevant output range so a single firm can serve the market cheapest, unregulated monopoly pricing creates deadweight loss, but breaking the firm into competing pieces would raise costs. Price regulation can set price equal to marginal cost with a subsidy to cover losses, price equal to average cost so the firm breaks even with no subsidy, or a price cap that rises with inflation minus an efficiency factor, giving the firm an incentive to cut costs. Rate-of-return regulation allows a fair return on capital but can induce over-investment in capital, the Averch-Johnson effect, because a larger capital base justifies larger allowed profits. Yardstick competition compares a regulated firm with similar firms elsewhere to set targets without needing to know its true costs.

Regulation also addresses externalities through standards, permits and liability rules. Command-and-control standards mandate a technology or an emission limit, which is simple to enforce but inefficient when abatement costs differ across firms, because it does not equalise marginal abatement costs. Tradable permits cap total emissions and let firms trade allowances, so abatement occurs where it is cheapest and the permit price equals marginal abatement cost, achieving a given environmental target at minimum cost. Collusion and anti-competitive conduct are regulated through competition policy: prohibiting cartels, reviewing mergers that substantially lessen competition, and policing abuse of dominance such as predatory pricing or refusal to supply. Regulatory capture is the central government failure: regulated firms, with concentrated stakes and expertise, influence regulators more effectively than dispersed consumers, so rules drift toward industry interests. Good regulatory design therefore includes independence, transparency, sunset review and attention to incentives, not merely good intentions. Information regulation, including disclosure requirements and labelling, is the lightest intervention and works best when the failure is asymmetric information rather than market power or externalities.

Public revenue and taxation

Public revenue comes mainly from taxation, with non-tax revenue from fees, public enterprise profits and asset sales, and borrowing covered separately as deferred taxation. Taxation is judged on four criteria that often conflict: efficiency, minimising distortions to behaviour; equity, distributing burdens fairly; adequacy and stability of revenue; and simplicity and administrability, including compliance and enforcement costs. Equity splits into horizontal equity, treating equals equally, and vertical equity, treating unequals appropriately unequally, usually through progressive rates where the average tax rate rises with income. The ability-to-pay principle bases tax on capacity, while the benefit principle bases it on benefits received from public services, which suits user charges better than general taxation. Direct taxes fall on income and wealth and can be progressive but are harder to administer in informal economies; indirect taxes fall on expenditure, are easier to collect, but tend to be regressive because poorer households spend a larger share of income.

Incidence is who really bears a tax, which depends on elasticities, not on who legally remits it. A tax on a good with inelastic demand is largely borne by consumers through higher prices, while a tax on a good with elastic demand is largely borne by producers through lower net prices. In general equilibrium, taxes shift across markets as factors move, so partial equilibrium incidence can mislead. The excess burden, or deadweight loss, of a tax is the welfare loss beyond revenue collected, arising because the tax distorts choices; it grows roughly with the square of the tax rate and with the elasticity of the taxed base, which is why broad bases with low rates are more efficient than narrow bases with high rates. The Ramsey rule for commodity taxation says efficiency requires taxing goods in inverse proportion to their elasticities, so inelastic goods bear higher rates, though equity considerations often override pure Ramsey prescriptions for necessities. Optimal income taxation balances redistribution against labour supply distortions, and the Laffer curve observation that revenue eventually falls as rates rise beyond a point, because the base shrinks, is a reminder that rates and revenue are not monotonically related, even though the revenue-maximising rate is an empirical question and usually well above zero.

Public expenditure and public debt

Public expenditure is evaluated by whether it corrects a failure, redistributes as intended, or stabilises the economy, and at what cost. Cost-benefit analysis is the central appraisal tool: list all social costs and benefits over the project life, value them at shadow prices that reflect true opportunity costs where market prices are distorted, discount future flows to present value, and accept projects with positive net present value. The discount rate is contested because it embodies judgements about intergenerational equity and the opportunity cost of capital; a high rate favours projects with quick returns and penalises long-lived environmental and infrastructure projects. Distributional weights can be applied to benefits accruing to poorer groups, but they must be made explicit rather than hidden in the appraisal. Expenditure can also be classified as productive, such as infrastructure and education that raise future output; redistributive, such as transfers and subsidies targeted at low-income groups; or stabilising, such as unemployment benefits that rise automatically in recessions. Wagner law observes that public spending tends to rise as a share of income as economies develop, while the displacement effect describes ratchet-like jumps after crises that are not fully reversed.

Public debt is government borrowing to finance deficits, and its burden depends on who holds it, what it finances, and growth relative to interest rates. Internal debt is owed to domestic residents, so interest payments are transfers within the economy rather than a net loss of resources, though they still redistribute and can crowd out private investment. External debt is owed abroad and requires future export earnings or reserves to service, creating a genuine resource transfer. Debt sustainability requires that the debt-to-output ratio stabilise: if the interest rate exceeds the growth rate, a primary surplus is needed to prevent the ratio rising indefinitely; if growth exceeds the interest rate, a modest primary deficit is consistent with a stable ratio. Ricardian equivalence argues that forward-looking households, anticipating future taxes to repay debt, save the proceeds of a tax cut financed by borrowing, so debt and tax finance are equivalent; the argument fails when households face borrowing constraints, have finite horizons, or do not fully anticipate future taxes. Debt can also be inflated away or defaulted on, but both damage credibility and future borrowing costs, which is why sustainability is judged by markets as well as by arithmetic.

Public budget and fiscal policy

The public budget records planned revenue, expenditure and borrowing, and the fiscal stance summarises its effect on aggregate demand. The headline deficit is revenue minus expenditure including interest payments; the primary deficit excludes interest payments and shows the current fiscal effort; the revenue deficit shows whether current revenue covers current spending, a concern when borrowing finances consumption rather than investment; and the structural or cyclically adjusted deficit removes the effects of the business cycle to reveal the underlying stance. Automatic stabilisers are budget features that dampen cycles without new decisions: tax revenues fall and transfer spending rises in a recession, cushioning disposable income, and the reverse occurs in a boom. Discretionary fiscal policy changes tax rates or spending deliberately, and its effectiveness depends on the multiplier, crowding out through interest rates, openness through imports, and whether the economy has idle capacity or is at full employment.

Fiscal rules attempt to discipline discretion: balanced budget rules, deficit ceilings, debt brakes and expenditure ceilings each trade off credibility against flexibility. Rules work best when they target structural balances, allow escape clauses for genuine emergencies, and are monitored independently; rigid annual balance rules can force pro-cyclical tightening in recessions, worsening the downturn they were meant to prevent. Fiscal federalism addresses which level of government should tax and spend: the assignment principle gives local governments functions with local benefits and limited spillovers, while redistribution and stabilisation, which leak across borders, belong to central government, with intergovernmental transfers correcting vertical and horizontal imbalances. The flypaper effect, where grants to governments stimulate spending more than equivalent income gains to residents, and the soft budget constraint, where lower governments overspend expecting central bailouts, are classic federalism problems. Sound fiscal policy therefore combines a sustainable long-run anchor with short-run flexibility, transparent accounting that distinguishes investment from consumption, and institutions that make commitments credible without making them unbreakable.

Types of goods

Deficit concepts

Instruments for externalities