I think my terse reply emphasized the wrong point and was completely misunderstood. Sorry.

I am not saying to maliciously lie about being underpaid, nor about non-salary compensation to your new potential employer. What I am saying is that during the initial negotiating process, when they ask "how much did you make at your last job?", if you suspect they might try to low ball you or negotiate you down, then you can maintain the advantage by lying and telling some arbitrary higher amount. Although if this is happening to you, you probably might want to look else where for a job. Unfortunately the economic reality means that is not always possible—who hasn't accepted at least one job from an employer they would not ideally choose to work for?

This thread and my reply is about the well-known claim that in any salary negotiating process, who ever first lets slip a specific dollar amount loses the advantage in the entire process. My reply was simply to point out that the entire logic is premised on a flaw, namely that you, the job candidate, are the one telling the employer how much you used to make, and then naming that amount becomes equivalent to losing the advantage of "don't make the first move." Since in most cases your new employer has no way to even verify what your previous salary & compensation was, they are utterly reliant upon trusting that you are telling them the truth. I have no idea what later commentors were saying about telling your new employer what your previous taxes were. I have never heard of any employee being forced to share their tax info with future employers. (No doubt there are some professions and jobs where this happens, such as those elected to public office or serving the public interest.)

My point was this:
in any negotiation process involving money it is a mistake to implicitly assume either party wants to be perfectly honest to their own disadvantage. If you look at any economic process like salary negotiation through the mathematical lens of Game Theory, you would never expect any "game player" to give away such an easy advantage.

Now I know this is going to offend many because it stabs the heart of the economics driving what we (falsely) believe is a strictly "ethical" matter, but please hear me out. I say we are all "small thieves" in our own context-dependent ways, because there really is no such thing as an objective "price." Rather, all prices are simply an arbitrary amount somebody is "willing & able" to pay. Any time you buy or sell, you first have to determine how much you can get from the other party. We are all skimming off the top of somebody else's profit margin, no matter how small.

No salary negotiation I've ever heard of followed this logic:

Recruiter: "how much did you make at your last job so we can trick you into making the first move and losing the advantage in this Game Theory-based negotiation?"

Candidate: "how much are you willing to pay?"

Even though in reality that is precisely what both sides are already trying to do. Size each other up and determine if both parties can agree to mutually benefit within their financial constraints. It's economics 101. But neither party will be honest and tell themselves nor the "opponent" that is what they are doing. And that's equivalent to lying—like Mark Twain said: "the worst lies are told in silence." And that is why I say we might as well throw out any ethical preconceptions and just look at it as a strictly game theoretic, economic process.

Since I don't even view this through the lens of ethics, I can playfully throw around the term "thieves" as a way of winking at the rules of the game itself. Who hasn't played cops & robbers and had fun pretending to be the robber?

To further see my point, think about the exact same situation, but inverted: if you, the candidate, were to ask anyone under the new potential employer: "how much did you make last year?", could you expect anyone to tell you?
Or ask the CEO: "I might want to work for you, but how big was your bonus last year?"
The conversation would come to a screeching halt right there.

In our era of Too Big to Fail, where the average CEOs makes hundreds of times the average salary of their lowest paid employee, why do so many of us "worker-bee" types have such a problem with turning the tables and fighting fire with fire? How do you think the CEO and the big guys got so big? How do you think the global Labor movement achieved so many gains on behalf of workers back in the 1920's? Why shouldn't employees be able to do the same today on a smaller scale? Fair is fair afterall.

That is all I'm saying. Stop voting down my insights just because I explained myself poorly and it sounded like something morally offensive to your biases. Where's the fun in having biases if we can't debate them on the Internet. :)