The working immigrant and social mobility in America

Let us look at the analyses of job growth in the past ten years and projected into the 2010 and ponder how job trends are reinforcing barriers to upward mobility.
They show an hourglass shape: strong, in some instances spectacular growth of knowledge economy jobs, shrinkage of routine jobs (such as office workers) and steady growth of many manual jobs. I have noted the influx of relatively small numbers of highly educated foreigners into the American workforce, for instance physicians.
David Autor of MIT in examining these trends says the American workforce is being polarized. (I have noted Autor’s findings here.)
The more we delve into this trend, the more we see structural changes that inhibit upward migration of low income workers. That does not mean we are doomed to a good jobs/lousy jobs future. It does mean, however, that government policy must be harnessed to lessen these rigidities.
The polarization challenge is at its most acute within the huge undocumented workforce of America. Handcuffs, not a handshake or even a handout, are looming into the futures of these workers.
We are losing through off-shoring net about 300,000 routine office types of jobs a year. We are adding net about 300,000 undocumented workers a year. Today undocumented workers are about (per the Pew Hispanic Center, with some adjustments) about 7.5 million undocumented workers — illegal immigrants — a year. they make up a quarter of the workforce in some job, particular high risk, such as roofers. One half (!) of new immigrants in the U.S. are undocumented workers. (I have presented Pew data here and here.)
It is important to realize that these manual jobs are increasing, and will continue to increase. Would anyone disagree with the proposition that an undocumented worker enjoys significantly less upward mobility than does a legal American working alongside him or her, or a legal immigrant?