GDP doesn't explain whether infrastructure projects are sustainable or not. You have to at least look at debt to GDP ratio. The thing about the 50's prosperit

GDP doesn't explain whether infrastructure projects are sustainable or not. You have to at least look at debt to GDP ratio. The thing about the 50's prosperity is that it derives from the federal and international theaters: The US won the war, and it went into debt to do so, but in exchange got willing borrowers. This was the formation of the military-industrial complex Eisenhower spoke of: Infrastructure projects with military application got a lot of support from both government and business. Among these was the interstate highway system, one of the landmark projects of the 50's, and one with military application. As a result of the new highways, municipalities all of a sudden had this form of growth driven into them through infrastructure that wasn't on their balance sheets, and a lot of pent-up demand for housing from the Depression and war years. Automobiles were ready for widespread use. All they had to do was approve more housing starts and millions of people suddenly could afford homeownership. That is the unique new thing that happened, and it can't be reflected just in GDP. But...if the whole premise of the highway system is based on borrowing, it's a house of cards waiting to fall. People can get their homes in the 50's, become bigger consumers in the following decades...debt to GDP falls sharply as the gains of building are reaped, and then the infrastructure bill starts coming due in the late 70's. At that point debt to GDP starts climbing again, but now the emphasis is on kicking the can down the road, not on renewing national infrastructure. "No more pork barrel spending" is a mantra of the Reagan era and beyond, as is an emphasis on outsourcing and lower taxes over long-term investments in the domestic workforce. It remains easier to build new than to maintain old. And all the while the debt ratio - at the national level - is climbing and climbing. There is still a lot of federal money going to those highways. But just borrowing and kicking the can down the road ain't enough to keep them. So Strongtowns can still be correct, if you zoom out a little!