Switzerland is an amazing place, not least the skiing, the chocolate, and the punctual trains. The latter is part of the country’s exquisitely maintained infrastructure: there are no potholes, and no deferred maintenance of train tracks, tunnels, airports, or public buildings. Few countries go so far, but many can take a lesson: it pays to maintain infrastructure at least so that it doesn’t fail.

We bring this up now because financial markets are telling us that it’s a very good time to build and repair infrastructure: real (inflation-adjusted) interest rates have fallen so low that it has become exceptionally cheap to finance the improvement and repair of neglected roads, bridges, transport hubs, and public utilities. Yet, in the United States, we are doing less public investment than ever: net government investment has fallen to what is probably a record low...