How Should We Teach Public Goods Theory?

Joshua Hendrickson recently wrote about the provision of public goods, and how we teach public goods in economics. My post today is not so much a reply to Hendrickson, but is inspired by his mediation on public goods as I gear up to teach another semester of Public Finance.

The theory of public goods that economists discuss among themselves is pretty straightforward: when a good is both non-rival and non-excludable, there is a strong case for government intervention of some sort (though not necessarily public provision). The opposite is true when a good is both rival and excludable: there is a strong case for laissez faire.

Seems simple enough, right? But communicating this concept to undergraduates and the general public has been a major challenge. Part of the confusion arises from the term itself, “public good.” Non-economists tend to use the term interchangeably with the notion of “the common good, as is clear from Wikipedia, a dictionary, or a conversation with your grandma. For this reason, I sometimes substitute the awkward phrase “collective consumption good” (this is actually Samuelson’s term in his classic article on the topic), but all the textbooks so use it so I often default to the standard terminology.

From Jonathan Gruber’s Public Finance and Public Policy

But I think there’s a deeper problem than just terminology. Economists have put themselves in a box. Literally. Here’s a standard 2×2 matrix from Jonathan Gruber’s undergraduate public finance textbook. I don’t mean to pick on Gruber here — this is a pretty standard presentation. You can find it in many microeconomics textbooks too, or on Wikipedia. Everything goes in a box! It’s a nice stylized way to think of the terminology. It makes for nice test questions. But here’s the real problem with it as a pedagogical tool: it doesn’t seem to help many students! Or at least, it doesn’t seem to help them retain the knowledge between their micro principles courses and upper division courses (at least in my experience, I’d be happy to hear others chime in here).

So how can we teach this concept better? I have a few ideas. I’d like to hear yours too.

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