Yet the overall cost premium, based on the difference in absolute wages between the U.S. and China, is actually expanding, so labor arbitrage involving China and other low labor cost markets will likely persist.

FORBES: Manufacturing May Be Coming Back to the U.S., Long-Term

For workers in industries -- for workers in industries that have been hard-hit, we'll help make up part of the difference in wages between their old job and a temporary, lower paid one, while they receive re-training that will help them find secure new employment at a decent wage.

CNN: McCain: Change is coming

One measure is the difference between slaves' wages and those of free workers with the same skills.

ECONOMIST: Economics focus

But his wages made no difference to the extent of his efforts around the house.

ECONOMIST: This just in: men are selfish layabouts

In some cases it started off as a form of wage restraint in the dark days of the 1990s: companies cut basic wages and employees hoped that performance-related pay might make up the difference, which it did not always do.

ECONOMIST: Still work to be done

Studies comparing wages in American cities with and without lots of foreigners suggest that they make little difference to the income of the poorest.

ECONOMIST: Of bedsheets and bison grass vodka