I've seen in it many non unionized shops. And there are plenty of examples you can find of promotions that seem unwarranted. Nepotism is a common reason. As

I've seen in it many non unionized shops. And there are plenty of examples you can find of promotions that seem unwarranted. Nepotism is a common reason. As is just general networking. Seems common for folks to get good at networking and generally pleasing management as much as doing a great jobs. I'd be delighted to see data on this. My prior is that it is rather evenly mixed with no obvious cause.