Catherine Ramsdell reviews Someplace Like America: Tales from the New Great Depression:

Consider—in 1979 “Wal-Mart employed 21,000 workers”, “General Motors employed 618,000”, and “the average CEO…was paid 35.2 times what an average worker was paid”. Flash forward to 2008 (and draw your own conclusions): “Wal-Mart employed 1.4 million”, “General Motors employed 92,053”, and “the average CEO…was paid 275.4 times what an average worker was paid…”

You can certainly make the argument that many of these manufacturing jobs were replaced by jobs in the tech sector.  The “IT field,” for example, wasn’t much of a field back in 1979, and now it’s ubiquitous.  

But there’s also an important difference between these two fields: the manufacturing jobs offered by General Motors in 1979 provided people without a college degree a “family” wage (thanks in part to the efforts of the UAW).  A 1979 high school graduate with a willingness to work hard could walk into a GM factory and ask for a job, and be reasonably certain they’d be provided with a good wage.  

A 2011 high school graduate, on the other hand, cannot simply walk into an IT shop with a strong work ethic and receive a job.  You need to have at least a couple years of post-secondary education to work in IT.  And given the fact that not everyone can be said to possess the talent or innate ability necessary to understand the intricacies of a tech sector vocation, those same high school graduates now must accept a job working at Wal-mart, where they will earn just-above minimum wage, and can expect to be encouraged by their wildly profitable employer to apply for public assistance instead of being provided with health insurance and other common benefits, even though Wal-mart could easily afford to pay their workers $12/hour with a resultant price increase to consumers of $0.46 per shopping trip.

So in essence, we’ve traded family-wage jobs with very few education and/or skill-based barriers to entry, for a) tech sector jobs that have at least some education and/or skill-based barriers to entry for a significant portion of the population, and b) jobs at Wal-mart that pay signficantly lower wages to employees who could’ve worked for General Motors in 1979 for a much better wage.  If you want to know why the middle class in America is shrinking, you have your answer.