That 70s Economy
I will admit to a small bit of cherry picking in this, but here is manufacturing employment across the 10 counties of Southwestern Pennsylvania between 1971 and 1979. I think it's fair to get past a bit of a bump resulting from the Vietnam War and what was generally considered an overheating economy at the end of the very end of the 1960s. This is what you get for employment that pretty much covers the regular seasons leading to the first 4 Steeler Superbowls. (Superbowl XIV was all of January 20, 1980)
So if you think there was some big and obvious trend down over this period, I don't see it. I would almost argue that manufacturing employment for the region in the 70s was less volatile than most any decade before. There was tremendous volatility in manufacturing employment in the region over almost every previous decade. The 70s were pretty stable here in comparison. All the more remarkable when you consider the economic tumult in the national economy during the 1970s. Stagflation anyone?
In fact manufacturing employment here was trending up near the last 4 years of that graph. Which may hint at the disconnect. Some of that trend was the Volkwagen plant starting up. So diversification in a sense and basic steel itself was not growing for sure. Only for Pittsburgh would a shift from an automobile dependent steel industry to the automobile industry itself be considered diversification. 'Diversification' we paid a pretty penny for mind you.
If you are still unconvinced that the public,along with the powers that be, t thought manufacturing was strong, and would continue to be the mainstay of the region's economy.... Check out these headlines from the middle of that period. Sept 1974: Area Economy Reported Strong. Or better yet from January 1975: Steel is Pittsburgh's Hedge on Recession. That the sun appears larger just before sunset is also an illusion.