Salary Surveys and Comparisons
In an attempt to prevent a proliferation of questions about the utility of certifications, or questions about which certification improves marketability or wages the most, let's collect relevant salary surveys here.
Why This Question Shouldn't Be Closed
Lists, especially lists of links, are generally off-topic on the Stack Exchange network. However, because this is such a frequently-asked question, it seems useful to have a single question to reference when duplicate questions are asked--and they will be asked, even if they're duplicates.
In addition, this question provides the community a single place to collect useful answers that can provide a starting point for additional research. With that in mind, references should be targeted and factual, rather than generic links or pointers to opinion pieces.
It is important to note that the very nature of this question doesn't allow for a single objective answer (or even a set of objective answers) that will remain true in perpetuity, so please don't take any of the data presented here as the "final word" on the subject. There's no substitute for common sense or critical thinking, especially on matters related to statistics or important career decisions.