In my experience (and this is only <i>my</i> experience&#x2F;observations) it is extremely unprofessional to bring up a coworkers salary in your own negotiations, for several reasons.<p>Many companies still have policies against coworkers sharing salary information. Yes, this is illegal in the US, but practically speaking: it being illegal is about as effective as requiring traffic police to have a &quot;preponderance of wrongdoing&quot; to perform a traffic stop. It still happens near constantly, and the cost&#x2F;benefit of trying to enforce these laws <i>in most cases</i> isn&#x27;t enough to actually pursue. (if you were to try and file a cause of action against your workplace for such a violation, you would surely mark yourself to future employers as being litigious - i.e you would paint yourself as a trouble-maker, so the benefit to doing so would have to be pretty big).<p>Secondly, social conventions don&#x27;t really provide an incentive for near-strangers (and that&#x27;s what many coworkers are for much of their careers) to share salary information. Yes, game theory says everyone wins if everyone shares, but we live in a society that is super prone to being offended. I don&#x27;t even think it&#x27;s polite to discuss money with friends.<p>As other posts on HN have stressed over the years, what really gives someone power in negotiations is a &quot;Best Alternative&quot; or BATNA[1].<p>[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Best_alternative_to_a_negotiated_agreement" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Best_alternative_to_a_negotiat...</a>