Why are semi-public goods called semi-public goods? Why and how do they differ from full public and private goods? (Here you should explain using the terms "public domain" and "externality"

Why are semi-public goods called semi-public goods?

Many goods provided by public and private sector are neither public or private. Instead they can be considered semi-public or semi-private depending on the preferences. Goods can be public or private, or anything in between. What does it mean? It’s probably not what you think. It doesn’t primarily mean who provides the product. In other words, a good is not private because it is provided by private businesses. A good is not public because it is provided by the government. Rather, private/public is more a description of how these goods are consumed.

A Semi public good is a near-public good that is it has many but not all the characteristics of a public good. Semi public goods are:

• Semi-non-rival: For an example, extra consumers using a park, beach or road do not reduce the space available for others. Sometimes beaches become crowded as do parks and other leisure facilities. Open access Wi-Fi networks become crowded
• Semi-non-excludable: It is possible but often difficult or expensive to exclude non-paying consumers. For an example, fencing a park or beach and charging an entrance fee, building toll booths to charge for road usage on congested routes

Why and how do they differ from full public and private goods?

Semi public goods have characteristics of both private and public goods, including partial excludability, partial rivalry, partial diminishability and partial rejectability. Examples include roads, tunnels and bridges. Markets for these goods are considered to be incomplete markets and their lack of provision by free markets would be considered to be inefficient and a market failure.

For example, private enterprise could provide some bridges, roads and tunnels if a charging system could be applied which solves the free rider problem. However, it is unlikely that all an economy’s (households and firm’s) need for transport and infrastructure could be met this way. Indeed, toll charge systems could be regarded as inefficient in that traffic slows down to pay at the toll booth, and traffic builds up causing congestion and increased external costs. However, the introduction of new technology, such as ‘smarter’ payments systems and number-plate recognition technology means that the free rider problem can be reduced or eliminated and the price mechanism can operate. Hence, over time, technology can convert public goods to quasi-public goods, and eventually to private goods.

Now, the complexity of the intellectual property concept of the public domain is that it encompasses both a place of production and a place of consumption, and it relates both to traditional economic activities and to traditionally non-market activities.

Externalities exist when the actions of one person or entity affect the existence and well-being of another. In economics, there are four different types of externalities: positive consumption and positive production, and negative consumption and negative production externalities.

We all know that A public good is one where one person's consumption doesn't prevent anyone else from consuming it too. In between public and private goods are externality goods (or semi-public goods). In some cases, benefits go beyond the individuals who consumed the externality good. One example is health expenditures. People in a community at large benefit when others get vaccinated against disease, since people won’t be infected by people who are vaccinated. In other cases, costs are imposed on people other than the ones who produced the externality good. Suppose you go to a park for a picnic, and you bring your iPod and external speakers. You play music during the picnic, which others in the park find objectionable. Your music reduces the quality of other park visitors’ experience.