Web sources, consultants, word of mouth, and formal surveys are all sources of information used to determine competitive position in compensation. We have all heard the phrase, "I am underpaid." And, many of us have heard the response, "If you can get it elsewhere, go for it." So what market data is most relevant to determine a competitive position, and competitors.
****The real question debate is****: select one source on which you would rely for competitive market data and why you would choose that source.
I would select www.salary.com. They offer lots of salary information by type of occupation and by geographic areas.
While you have to pay for the really good research, they have free information. In addition you can sign up for an employer trial account. They have 7000 company members and 10,000,000 employee members.
Salary.com builds on-demand software around a deep domain knowledge in the area of compensation to help customers win the war for talent by simplifying the connections between people, pay and performance. Salary.com's cutting edge technology is integrated with actionable data and content, empowering customers to make the best decisions about pay and performance and help them to attract, motivate, reward and retain top performers. "
Source -- www.salary.com
Here is a description from Alexa.com that ranks websites --
Compensation information online. Free salary information, salary and benefits advice, career and job search help. Hundreds of salary surveys, ...
The cited solution provides a comprehensive review from several sources for a well known salary search website.