People can write what they like on their blog, but this article seems to be missing key details - we don't find out what the model is or the coefficients he's using and the model apparently immediately produces unrealistic results. Hopefully it is made clear in the book, but unless someone has read Abundance it is hard to follow.

If the model is just a rough rule of thumb then spot checking 4 cities in completely different legal frameworks, cultures and economic situations doesn't give us a lot of data. Economies are very complicated and any effect can be overruled by something unrelated but more impactful happening.