I have said it before and I say it again.
HR will always ask you to keep your pay confidential because the
company will want to squeeze you as much as possible.
If they can pay less for more experienced workers, they
will.
And a lot also depends on your luck and at which point of the
economic cycle that you graduated at.
Eg. You graduated during an economic downturn.
Salary offered then is $1,800. You work for 2 years in that
company and get a promotion/salary adjustment after that 2 years to
a salary of $2,200. However, at that point in time, the
economy rebounds and a new fresh grad enters your company and does
a similar job to what you are currently doing. Guess how much
she will be paid? $2,200.
Do you think the company HR will adjust your salary higher than
the fresh grad? If you are lucky, they might give you another
$100 extra. If not, they will quietly tell you to keep your
$2,200 salary confidential because they don't want you to ask
around why you are being paid the same as an inexperienced grad
even though you have 2 years of experience.
Yes sir.
That's the way the world works. 
