By co-workers do you mean people in your same position or you mean you also walk in to your bosses office or your bosses bosses offie and ask them how much they make? Other than companies with unique cultures, I would imagine very few would do that (or get a pleasant response), but if amounts are listed on job descriptions you would know how much everyone above you is making. Even asking 'co-workers' how much they make would vary greatly based on the type of company and job you work in, where that would be deemed acceptable behavior, or result in the person happily telling you. As would also depend on if the person you are asking makes more than you or less, if more they would presumably be less likely to tell you or tell your as honestly.