I don’t think you need reliable data to support that claim. It’s kind of self-evident. Just go to any large-scale U.S. manufacturing operation and see how few people it takes to work there compared to a generation ago. You used to have entire company towns where thousands of men would work at the local plant. Today, these plants produce just as many units of whatever they produce, with a much smaller work force.
You need some hard data to support this statement:
Kudos to the Freeper who pointed out several months ago that U.S. manufacturing employment would have been declining for years even if the U.S. was the only country in the world, and there was no such thing as "foreign trade."
Many facts refute the above, including:
1. There are many more individual manufactured products produced now than in the past.
2. People own more stuff now, more vehicles, more TVs and more gadgets of both old and newer technology.
3. The US population has increased from about 200 million in the 1960s to about 320 million now.
As I said, the only stat that would really tell us anything about this is one that shows how many manufacturing jobs were required to produce all the manufactured products sold in the US in 2015, and say, several different years going back to the 1960s?