Imperfect market information - Market Failure

Asymmetric information exists when one party in a transaction has more or better information than the other party (1). This gives the better-informed side an advantage it can exploit — for example, the seller of a used car knows its faults while the buyer does not (1).

A merit good is a good that is under-valued by consumers and therefore under-consumed relative to the socially optimal level (1), because consumers do not fully appreciate its long-term private and social benefits (1).

For example, education is a merit good: individuals under-estimate how much it will raise their lifetime earnings and productivity, so they under-invest in it (1). It also generates positive externalities — a more educated, productive workforce benefits wider society (1).

An information gap (imperfect information) means consumers lack full or accurate information about a good's true costs and benefits, so they cannot value it correctly and choose the wrong quantity.

In the market for cigarettes, consumers underestimate the long-term private costs (the future health damage, addiction and reduced life expectancy) and the negative externalities (passive smoking and the burden on health services). Because they under-estimate these costs, they over-value cigarettes.

As a result, consumers demand and consume more cigarettes than is socially optimal — cigarettes are over-consumed. Too many scarce resources are therefore devoted to producing them, so there is a misallocation of resources.

This misallocation is the definition of market failure: the free market, left to itself, produces and consumes a quantity that does not maximise society's welfare. Cigarettes are therefore a demerit good, which is why governments intervene (for example with taxes) to reduce consumption toward the social optimum.

Asymmetric information exists where one party knows more than the other. In the insurance market, the buyer knows their own health, lifestyle and risk far better than the insurer — the information advantage lies with the buyer. This imbalance leads to a misallocation of resources through two connected effects.

Adverse selection. Because the insurer cannot distinguish high-risk from low-risk customers, it must charge a pooled (average) premium. That premium looks like good value to high-risk buyers and poor value to low-risk buyers, so the market attracts a disproportionate share of high-risk customers — it 'selects adversely'. Claims then rise, the insurer must raise premiums, and more low-risk people withdraw. The pool worsens further, and safe consumers who would benefit from cover are priced out — a misallocation, because trades that should happen do not.

Under-provision of a beneficial market. As premiums spiral and low-risk buyers exit, the insurance market can shrink or partly break down. Insurance is itself a merit good (it protects households against disaster and has wider social benefits), so its under-provision means resources are misallocated away from a socially valuable service.

Diagrammatically and logically, the root cause is the buyer's information advantage: without it, insurers could price each customer's risk accurately and the market would clear efficiently. Because they cannot, the outcome is an inefficient allocation — a clear case of information failure. (This is distinct from moral hazard, where holding insurance changes the insured person's behaviour.)

Junk food is a demerit good: consumers over-value it because they under-estimate its long-term private costs (obesity, diabetes) and its negative externalities (the burden on health services), so it is over-consumed relative to the social optimum — a market failure caused by an information gap.

The main effects of an information campaign. By providing accurate information (labelling, health warnings, advertising), the campaign aims to close the information gap so consumers value junk food correctly. If successful, consumers revise their preferences and demand less: the demand curve shifts left, cutting consumption toward the social optimum. Unlike a tax, this tackles the root cause (the mis-valuation itself) rather than just the price, so any fall in consumption is more permanent, and it preserves consumer choice and avoids the regressive effect of a tax. It may also generate positive spillovers — better public health lowers future health-service costs.

Evaluation — how effective, and at what cost? First, effectiveness is uncertain: information campaigns are often ignored, especially if junk food is cheap, tempting and habitual, so demand may shift only a little. Second, there is a time lag — changing entrenched preferences is slow, whereas a tax bites immediately. Third, the campaign has an opportunity cost: the money could fund healthcare or education, and there is a risk of government failure if it is poorly targeted. Fourth — the key normative point — deciding junk food is a demerit good rests on a value judgement that consumers 'ought' to eat less; some argue this is unjustified paternalism and that informed adults should be free to choose.

Judgement. An information campaign can help reduce junk-food consumption by correcting the information gap, and it is attractive because it preserves choice and is not regressive. However, its effect is likely to be modest and slow, and it depends on whether consumers actually act on the information. It is therefore best judged as one part of a wider package — combined with taxation and regulation — rather than a stand-alone solution, and its justification ultimately rests on a contested value judgement about how far the state should shape consumers' choices.

A merit good such as healthcare is under-valued and under-consumed relative to the social optimum, because an information gap means consumers under-appreciate its long-term private benefits and its positive externalities (a healthier, more productive population; fewer infections spread). A subsidy is a government payment to producers that lowers their costs, shifting the supply curve down and to the right, cutting the price consumers pay and raising the quantity consumed. The question is whether this is the best way to raise consumption.

The case for subsidising provision. By lowering price, a subsidy causes an extension in demand along the demand curve, so more healthcare is consumed — moving output toward the social optimum and internalising the positive externality. It is well-suited to a merit good because affordability is often the barrier: cheaper (or free) provision reaches low-income households who would otherwise go without, improving both efficiency and equity. Wider society also gains from the external benefits (a productive workforce, lower disease transmission).

Limitations of a subsidy. First, the effect depends on the elasticity of demand: if under-consumption is driven by poor information rather than price, cutting the price may raise consumption only a little — the subsidy treats the symptom, not the information gap itself. Second, subsidies carry a large opportunity cost: the money must be financed by taxes or borrowing and could fund education or infrastructure instead. Third, there is a risk of producer inefficiency and government failure — providers sheltered by subsidy have weaker incentives to control costs, and the subsidy may be set at the wrong level or captured by producers rather than passed to patients.

Alternative policies to weigh. Because the root cause is an information gap, information campaigns and education may raise consumption more durably by shifting the demand curve rightward, changing how consumers value healthcare. Direct state provision (a public health service free at the point of use) guarantees access regardless of income. Regulation (compulsory vaccination, mandatory health insurance) raises consumption directly. Each has its own costs and enforcement problems, but they tackle the under-valuation that a subsidy alone leaves intact.

Evaluation and judgement. Whether a subsidy is 'best' depends on why the good is under-consumed and on the policy goal. Where the barrier is affordability, subsidised provision is highly effective and improves equity; where the barrier is an information gap, it must be combined with information provision to change how consumers value the good. There is also a value-judgement at the heart of the case — treating healthcare as a merit good assumes consumers 'ought' to consume more, a normative position some may contest. On balance, subsidising provision is a powerful but not sufficient tool: it is most defensible as part of a package — alongside information campaigns and, where justified, regulation — rather than the single best way on its own.