In a recent post, commenter Jeremy H. helped point out that the use of the term “public good” is grossly abused in the case of transportation. Even Nobel economists refer to roads as “important examples of production of public goods,” ( Samuelson and Nordhaus 1985: 48-49). I’d like to spend a little more time dispensing of this myth, or as I label it, an “Urban[ism] Legend.” As Tyler Cowen wrote the entry on Public Goods at The Concise Library of Economics: Public goods have two distinct aspects: nonexcludability and nonrivalrous consumption. “Nonexcludability” means that the cost of keeping nonpayers from enjoying the benefits of the good or service is prohibitive. And nonrivalrous consumption means that one consumer’s use does not inhibit the consumption by others. A clear example being that when I look at a star, it doesn’t prevent others from seeing the same star. Back when I took Microeconomics at a respectable university in preparation for grad school, I was taught that in some cases roads are public goods. We used Greg Mankiw’s book, “Principles of Economics” which states the following on page 234: If a road is not congested, then one person’s use does not effect anyone else. In this case, use is not rival in consumption, and the road is a public good. Yet if a road is congested, then use of that road yields a negative externality. When one person drives on the road, it becomes more crowded, and other people must drive more slowly. In this case, the road is a common resource. This explanation made sense, but I was skeptical – something didn’t sit right with me. Let’s take a closer look. First, Mankiw uses his assertion as an example of rivalrous vs nonrivalrous consumption, while not addressing the question of excludability. Roads are easily excludable through gates […]
