I stumbled across this great slide presentation on U.S. manufacturing given by an economist at the Chicago Fed. The key points:
1) The decline in manufacturing jobs really parallels (though over a more compressed period of time) the decline in agricultural jobs.
2) Manufacturing employment as a percentage of national employment has been dropping for 60 years.
3) But manufacturing output has been growing faster than the overall economy since the early 1990s, though lower prices have meant manufacturing makes up a smaller share of gross domestic product.
4) Average annual productivity growth for manufacturing grew at a 4.2 percent annual pace from 2000 through 2006 vs. 2.7 percent for the rest of the economy.
What does it all mean? It means automation is what's really affecting manufacturing jobs. But domestic machines don't make as compelling a political target as low-cost workers in China and Vietnam.