The excuse employers make is that your past salary helps them determine your experience level, it pegs your value, and it helps them establish a new salary for you. By that logic, they don't need to interview you. All they need is your salary history and you're off to the races. By using the figures other employers have used, they'll know what their job is worth and what you are worth. And they'll win the lottery, too.
Salary is a judgment of value .
It's incumbent on an employer to figure out what the job he wants done is worth, quite apart from who you are, what you've done, or what you've been paid before. In the interview, the employer factors in his judgment of how you would contribute to the success of that job. That's how an offer should be derived. Skip the classifieds. The ads are the subtle beginning of an employer's effort to gain an edge in negotiations.