The local AFL-CIO affiliate has been running ads on the sports-talk channel as of late. One that was on this afternoon started something to the effect of "collective bargaining created the middle class." They might actually be more correct than my anti-Big Labor thought-patterns would think at first.
For a good chunk of the 20th century, the US was spare a lot of class warfare by being able to pay factory workers a wage on par with lower-level professionals like teachers and accountants. That created a large block of workers who had disposable income and didn't feel like a poor "working class" plebeian. They were rechristened the "middle class," neither noble nor commoner.
That gave 80% of the country something loosely in common. The folks in the 30th percentile didn't feel poor and the folks in the 80th percentile didn't feel rich; they were all "middle class." Store managers and store clerks could both feel like Fanfare for the Common Man was for them.
Would that have happened without unionization? Not as easily, as it is a bit harder for Joe Sixpack to negotiate for higher wages on his own, especially if he doesn't have a strong skill set. Unions can negotiate some wage increases out of companies, sometimes to a point of crippling companies; however, in earlier eras with less international trade, competition was not as fierce and wage increases could be passed on to customers in the form of higher prices.
Free trade isn't good for low-skilled workers, for they now have to compete with labor from poorer countries. Better-skilled workers still have an advantage in that such education is far from universal and fewer people can do their jobs; computers have allowed a number of professions to leverage their talents on a global scale. That creates a wider gap between factory-type workers and "knowledge" workers.
We're starting to see a breakdown in that "middle class" commonality, as it becomes harder for a high school grad without a good skill set to make a family-supporting wage. Getting that skill set is the kicker, which include a job to further refine it. Between a drop in unionization and increased competition via trade, we're seeing something of a sub-middle-class developing.
I don't have a good policy proscription for that. Protectionism and autarky (no trading) doesn't help much, nor does taking out frustrations on the haves. Lower taxes and regulations only help so much, for they might cause new jobs to be formed, but those jobs might not fit the people needing to get a foot into the door of the system.