Could an economic theory popularized in the 19th century revitalize 21st century Detroit? A lot of economists seem to think so, and I share their enthusiasm for both the land-value tax and its champion, the economist Henry George. Still, I have my doubts.

Under one version of the idea, which is supported by the city’s mayor, the tax on the value of buildings would fall from 2% to 0.6%, to be replaced by a 11.8% tax on the value of the land itself. The plan has potential, but it is worth laying out the costs as well as the benefits.