In government sector wages are easy to determine. Your seniority and experience determines your basic salary. Then based on the nature of the work, posting etc. your final pay package is determined. So effectively whenever a government servant states his designation, you can exactly know how much wages he draws.
In private sector, it is a bit awkward. The worker salaries are more or less standardized and everybody knows how much the other knows. The compensation package of the CEO and other top executives has to be disclosed to the shareholder (and hence public). Everybody knows Robert Nardelli received a $210m pay-off when Home Depot fired him for incompetence.

However what surprises me is that wages of the peers are rarely disclosed. What is so special about the white collar employees that their wages are never revealed? We all demand RTI (right to information act) in government departments when our workplace themselves lack it. I am a rational man, so I think there should be a sound logic behind all this.
Either the workers like you and me have a vested interest in not disclosing their salary. I am ashamed of the fat salary I draw and I do not deserve the bonus which the company gave me. Hence it is in my best interest to cover it up as much as possible.
Or the HR and management are screwing me. They pay me a quarter of what I deserve and hence they do not want me to be in the position to compare my salary with the others.
Since I cannot think of a third reason… lets analyze the 2 premises.
Worker: The Company would be a fool to overpay me. Even if due to a temporary market conditions I am getting more than what I deserve, the company will adjust it in the next pay review/hike or they might even fire me. Other reason could be that I live in denial and believe that I do not care about the wages.
Since both are weak arguments, I think it is the HR and management that want to deny me of this information. The management thinks that I do not know that my company pays that fresh graduate/new guy much more than what it pays me…
Government employees do not switch jobs that often because they know that they are getting a fair pay. Most job switches in private sector happen when the new company corrects the distortion and offers to give the employees what they rightfully deserve.
The constitution guarantees us “Equal pay for equal work”, almost all companies advertise “Equal opportunity employer”. Yet you give no evidence to prove/disprove this theory. Companies demand loyalty from the employees, but they spare no opportunity to con them.
Also do read this wonderful article. compensation and this