"In a recent study published by the Academy of Management Journal, Prof. Peter Bamberger of Tel Aviv University's Recanati School of Business and Dr. Elena Belogolovsky of Cornell University's School of Industrial and Labor Relations have published a study that explains why pay secrecy is likely to hurt an individual's work performance and prompt top talent to seek new employment. They conclude that pay secrecy weakens the perception by employees that a performance improvement will be accompanied by a pay increase. It also finds that high-performing workers are more sensitive than others when they perceive no link between performance and pay; suggesting that pay secrecy could limit a company's ability to retain top talent."
So who, if anybody, benefits from pay secrecy?
One thing worth noting: folks in the US generally have an absolute right to discuss their salary and benefits with co-workers or anyone else, company policy notwithstanding. Your status as a union member is irrelevant. http://www.lexisnexis.com/legalnewsroom/labor-empl oyment/b/labor-employment-top-blogs/archive/2013/0 2/21/you-have-the-right-to-discuss-salary-with-cow orkers.aspx [lexisnexis.com]
My private employer quietly rescinded a rule prohibiting salary discussions a few years ago after someone was disciplined for violating it.
That said whether you'll get truthful information from your colleagues and whether management will care that you make $X less than Carl remains to be seen.