it is a good general comparison. So you hv to take into account ur qualification, job scope and yrs of experience.
e.g. $2.5k @ age grp 25-29 = top 45%. if u r a University Fresh Graduate, you are getting average pay (fair enough). If u r a ITE grad, u r quite well paid. But if u experienced grad working late everyday, it is time to talk to ur boss.