I've seen how this works before, and what happens is all the companies submit their data to equifax, equifax then goes and creates a set of "profiles" for example "Junior software engineer", take all the data for employees with software engineer related titles and less than 3 years of experience, remove outliers and sell the result to employers as "salary band information". The result is that your employer gets a number saying "Junior software engineers in X location earn from 80,000 to 110,000" and that's used by your HR team to ensure that you don't drive up salaries by over offering. The role of equifax in this is to act as a level of protection, because the actual resultant behaviour is all the software companies working as a cartel to limit employee wages.
We rarely hear, it has been said, of the combinations of masters, though frequently of those of workmen. But whoever imagines, upon this account, that masters rarely combine, is as ignorant of the world as of the subject. Masters are always and everywhere in a sort of tacit, but constant and uniform combination, not to raise the wages of labour above their actual rate. . . We seldom, indeed, hear of this combination, because it is the usual, and one may say, the natural state of things, which nobody ever hears of.
