That was only possible because that time period was a window in which our technological superiority made it possible to provide the average working man with that standard of living. That period is coming quickly to a close.
Far more sustainable than the present, which involves unsustainable personal debts, unsustainable trade deficits, and unsustainable federal borrowing.
But please note that CENTRAL POINT OF THE ARTICLE explains WHY our technological superiority lessened, rather than moving exponentially further ahead.
It's only a closed system if you ignore the resources and cheap bottom-tier labor the first world extracted from the third world at a fraction of their potential value. The U.S. in particular was very active in this time period propping up puppet regimes around the third world in order to get cheap access to their raw materials and labor. The world has never been a closed system.
For the millions now with ZERO income, even Chinese-made Wal*Mart crap is unaffordable. Yet the unionized workers of the 1950s - 1970's somehow purchased cars, household products, and clothing like domestically-made Levis blue jeans WITHOUT slave labor from repressive countries and without borrowing trillions fro those same countries.
I will gladly trade somewhat higher consumer prices for confidence that I will be employable in safe conditions at a middle-class wage for the duration of my normal working life.
And I'm very pro-manufacturing: but the environmental externalities must be mitigated and properly priced: my health is very valuable to me, even if there's no clear market price for it.