> But chances are, no matter who you are, at any given time, you can't negotiate a 25% higher salary from a competitor. If you could have done that, why did you take this job in the first place?

Because you took it before you had your current level of experience or list of accomplishments that makes you worth 25% more money.

> It's not like there's some "union rulebook" that all unions must follow as soon as they come into existence, that says, "First, make sure absolutely everyone makes the same amount of money. Next, make really crappy employees unfireable."

There kind of is. What above average employees want is above average wages and competent peers. What below average employees want is average wages (i.e. more than they're worth). What really crappy employees want is to not be fired.

You can't have them all at the same time. So if the union nominally represents all of them, who is it supposed to throw under the bus? If the company can spend a given amount of resources on employees, which employees should get them? A union representing multiple types of employees inherently has that conflict of interest.

You can't just assume that the best employees will control the union. It's the worst employees that have the most incentive to make sure the union keeps them in their jobs -- the best employees can make the calculation that they're better off at a competitor without a union than to have to engage in constant struggle with not only management but also the other employees with conflicting goals.

> On the other hand, at any given time, the union is always going to be fighting for you to get reasonable raises based on your position, and will be available to help you show that you deserve a significant raise if your current compensation does not match the going rates for what you're actually doing.

How is that any different than what you can do on your own, or hire someone to do who doesn't have the conflict of interest of representing other employees competing for the same pool of company resources?

> This is ignoring all the other things unions do, that don't directly relate to compensation, like ensuring that employees aren't taken advantage of by the company in a variety of creative and quasi-legal ways.

That seems like the role of the various attorneys general.

> I think it's much more likely that, given the prevalence of attitudes such as yours, it would be primarily concerned with the aforementioned protections, as well as setting wage floors for given levels of expected performance, while leaving the ceiling free for people who, like you, think they can negotiate something better.

Then you're paying dues so they can negotiate higher wages for people who aren't you but come from the same pool of available employee compensation, leaving less for you when you still have to spend your own time/resources on top of that to negotiate your own compensation.

Good employees and bad employees have different interests. And if you put them together in the same union, the bad employees are usually more interested in not getting fired than the good employees are in making sure that they do -- because the good employees have plenty of prospects at other companies where they don't have to constantly struggle to keep their own union from acting against their interests.

Then good employees leaving impairs the long-term health of the company, which hurts even most of the employees left behind. (Though presumably not the ones that would otherwise have been fired for incompetence.)