How does SalaryFairy know what's correct? Just in general? Someone with a statistics background might have a better idea, but I'm thinking might help to allow

How does SalaryFairy know what's correct? Just in general? Someone with a statistics background might have a better idea, but I'm thinking might help to allow users to, in their profile (and have it be optional), enter their salary. That way, you'll not only be able to show people what other people think they should be making, but you might be able to (once a certain threshold is met) show what people with similar experiences in a certain region are making. And you'd be able to see how close the guesses are to the real thing and maybe figure out a margin of error. It might also be nice to allow people to put in descriptions of what they did at their workplaces. Someone doing embedded development might get a significantly higher salary than someone doing .NET, even if they have a similar # of years of experience.