|Rivalrous Consumption||private good||common resource, tragedy of the commons|
|Non-rivalrous Consumption||meh (e.g., some natural monopolies)||public good|
An example of an excludable and non-rivalrous good would be a movie theater room which is half-filled.
In this case, the cost to the owner or a patron of adding another person to the movie audience is zero, while the benefit is positive. So, some “social” benefits are unrealized, and there is deadweight loss. But the solution is scarcely for the government to subsidize movie theaters. It’s not a big deal in the actual economy. Hence, “meh”…
On the other hand, “excludable and non-rivalrous” applies to artificial scarcity-imposing laws, especially as regards copyright. My enjoyment of a certain digital book does not conflict with anyone else’s such enjoyment, given that a book, say a PDF file, can be copied at zero cost yet will yield a positive benefit. Yet the legal regime punishes people for copying copyrighted media. Seems economically inefficient, doesn’t it?