It's the type of economy. Economies grow and evolve. They go through stages. i.e. hunting, agriculture, manufacturing, service, information
The US has passed it's manufacturing stage (we're still #2 in the world though), is in it's service phase and quickly moving to information. We aren't going to see the return of the manufacturing stage, because frankly other countries can do it cheaper and always will. And as the global economy develops, it moves. So China might be firmly in their manufacturing stage now but in 50 years we could see a place like India or Vietnam, or a reborn North Korea as the leader.
But at the same time manufacturing is down globally. Everyone is dealing with it. It's down in Europe, it's down in Asia. Yet the US is still the second largest manufacturer in the world, at roughly $2 trillion in value added in manufacturing. First place is China at $2.7 trillion. But Japan is a distance 3rd at $917 billion. Mexico is 12th at $213 billion.
I think the biggest blow to pay rates, especially for union members, is the rise of the "right to work" and "non union" shit. My wife has run head first into that over the last 10 years as more and more jobs in her field have flat out flipped from union jobs with union rates to non-union or no-union-jurisdiction.
Overall I think the problem is that the global economy is equalizing out rates. And not even global, I just think we're at a point where the world has shrunk to where you find pay rates in places like NYC being in line with pay rates in Orlando. Where before it would vary due to local costs/taxes/etc. So now we in the US see pay go down, but someone in Vietnam sees it going up as things try to find a new equilibrium as the walls separating us go down (NAFTA/TPP/etc).
Sucks for us.