Which of the following scenarios best illustrates the concept of positive externalities in consumption, particularly in relation to welfare economics and public goods, and the role of government intervention?

A positive externality in consumption occurs when someone’s consumption of a good or service benefits others who did not pay for it. For example, when a person gets vaccinated, they not only protect themselves from disease but also help prevent the spread of illness to others, improving public health. This situation illustrates welfare economics because it shows how individual choices can lead to broader benefits for society. However, since vaccines can be under-consumed due to their costs, government intervention, like providing free vaccinations, can encourage more people to get vaccinated, maximizing the positive effects on community health. This is why the government often steps in to promote the consumption of goods that have positive externalities, ensuring everyone can enjoy the benefits.