In Microeconomics there are 4 types of externalities - Positive Consumption Externality, Positive Production Externality, Negative Consumption Externality, and Negative Production Externality. And along with externalities you learn about common resources and public goods which are classified according to their excludability and rivalry.
I believe that common resources go in the category of negative externality since they tend to be over-produced, and that public goods go in the category of positive externality since they tend to be under-produced.
What I'm confused about is whether common resourses are classified as Negative Consumption Externality or Negative Production Externality. The two have different characteristics that are represented by their different graphs, where the Negative Production Externality has two Cost Curves (Private Marginal Cost and Social Marginal Cost) and one Utility curve, while Negative Consumption Externality has two Utility Curves (Private Marginal Utility and Social Marginal Utility) and one Cost curve. I'm confused as to which negative externality common resources belongs to.
The same goes for public goods. Are public goods Positive Consumption Externality, or Positive Production Externality? Like the explanation written previously, the two have different features and graphs as well depending on whether it is consumption, or production externality.
So to sum up I guess I have two questions which are a bit similar:
Are Common Resourses classified as Negative Consumption Externality, or Negative Production Externality?
Are Public Goods classified as Positive Consumption Externality, or Positive Production Externality?
I would sincerely appreciate it if someone can provide me with a detailed explanation regarding each question. Thanks! :)