I misspoke. What I should have said is this.
For decades following World War 2, our country was thriving because our economy was based on our being a world leader in manufacturing goods.
And slowly and over time, other parts of the world began to compete with us (chiefly Japan, Hong Kong and Taiwan).
BUT, it wasn't until later on when our industrial and business leaders discovered the unlimited supply of dirt cheap labor China provided, that everything really started to change.
If you want to better pinpoint the time, find out what year it was when Sam Walton took down all those Donald Trump-sized signs in his stores which said "WE SELL PRODUCTS MADE IN THE USA".
That's when the downward spiral began. And that's what led to the "rust belts" and not just in Michigan and Ohio and that part of the country. It was shortly after that that the textile plant closed in Elkin NC where my first cousin had operated a car dealership very successfully for ten years.
And when that plant closed and the jobs went to China, it took most of the jobs in town with it and his car dealership went bankrupt.
That story was repeated over and over in all of the manufacturing regions of the country.
Because 50 cent/hr labor with no benefits looked a whole lot better to the business magnates than American union wages with benefits.
And the public went along with it because it let them buy products a lot cheaper than could be made with American union labor.
And this graph of yours correlates pretty well to the timeline of it...