The Compensation Problem

There is perhaps no question on the MBA application I hate answering more than telling schools my precise base salary+bonus.  At a basic level, I feel like my privacy is being undermined.  But there is also a far deeper concern as it relates to admissions.

Adcom states that compensation information is being gathered purely for "data" purposes.  Perhaps that may be true, but there is also the distinct worrisome possibility that they use compensation to roughly gauge how good you were at your last job and the extent of your career progression.  I am personally concerned about this for a number of reasons.  First, even though I spent much of my time in finance, my firm was rather small and not well-known, and the compensation structure was rather ungenerous to say the least.  Thus, my pay was a lot lower than other finance professionals for reasons that were totally beyond my control.  Second, will adcom see this as a lack of career progression or poor performance?  I had seriously considered using the optional essay to explain this, but I ultimately decided against it because I did not want to come across as whiny or give off the impression that my firm was not legit.  

I have gotten mixed responses on this from friends and admissions consultants.  It's too late to change things since I no longer work there, and I'm making even less money at my current startup (more upward potential however).  The only thing I can do is push forward and do my best in my current positions and in the execution of my applications.