A column in the New York Times notes that many economists "support Pigovian taxes because, in some sense, we are already paying them." In what sense might consumers in a market be "paying" a Pigovian tax even if the government hasn't imposed an explicit tax?

In economics, a negative externality is a cost incurred by third parties as a consequence of an economic activity they're not directly involved in. For instance, a factory emitting pollution affects the health of nearby residents, yet the factory doesn't necessarily pay for this impact. Similarly, when a smoker releases cigarette smoke into a public space, non-smokers breathe in secondhand smoke against their will and could suffer health issues as a consequence.

Despite not participating in the activity, these third parties bear expenses, such as medical costs or property value decreases, which aren't reflected in the market price of the good or service causing the externality. This results in a scenario where private transactions between buyers and sellers have unintended side effects on bystanders, leading to a discrepancy between private gains and social welfare.

The contrast between social cost and private cost is central to understanding the economic impacts of negative externalities. Private cost refers to the expenses faced directly by the producer or consumer engaging in a transaction. This includes materials, labor, and other production costs for businesses, or the purchase price paid by consumers.

On the other hand, social cost encompasses both private cost and any additional costs borne by society due to negative externalities. Using the factory example, the private cost includes the expenses of running the factory, while the social cost adds in the wider health and environmental cleanup costs induced by the factory's pollution.

The key issue arises when social costs are significantly higher than private costs, as the price for the commodity or service does not fully capture the true cost to society. Pigovian taxes aim to bridge this gap, ensuring that prices more accurately reflect the full cost of production.

Market correction mechanisms are tools used to adjust for inefficiencies within markets, particularly those created by negative externalities. Pigovian taxes are one such mechanism designed to mitigate the negative impacts of externalities by incorporating the social cost into the market price.

The idea behind these taxes is that by increasing the cost of producing or consuming a good or service that generates negative externalities, the market will adjust to reflect the true cost to society. In theory, this should lead to a reduction in the production or consumption of goods with high negative externalities, encouraging businesses and consumers to switch to alternatives with lower social costs.

Other mechanisms include subsidies, which can promote behaviors with positive externalities, or regulations that limit actions causing negative externalities. The effectiveness of these tools depends on how well they align private incentives with social welfare, and whether they can be implemented in a way that doesn't create additional market distortions or unintended consequences.