[efitz]

No, because they need to attract employees and employees would generally not be attracted to uncompetitively low compensation packages.

As a result, companies absolutely track how much employees of a type and level get paid elsewhere, so that they know where to aim compensation packages competitively.

[thinkharderdev]

Not sure if the parent's concern is valid but I think the argument would be that companies can conspire to all suppress wages so they don't have to compete on comp. That would be hard to do now because they can't "officially" conspire in this way (eg sign a binding contract with each other) because that would be illegal. Without an enforcement mechanism it is too easy for any one company to defect from the "gentleman's agreement" and offer higher wages. If all salary information was public though, then as soon as one company defected and offered one high-value employee a higher salary everyone else would immediately know it and start competing on salary again. So that makes the informal agreement more stable and leads to lower wages.