Kevin Drummakes a nice, and frequently overlooked, point about why unions matterfor reducing inequality.  The Church has gotten this for over a century:

If you're interested ingovernment policies that actively favor the working and middle classes,you need to have some kind of substantial political interest groupfighting on their side. That's Politics 101, and right now unions arepretty much all we've got. They aren't perfect, and they frequently actonly in their own narrow self-interest, but without them there's noorganized opposition to the agenda of corporations and the rich. Wartsand all, they're worth supporting until something better comes along.