Salary History?

I seriously doubt it - I live in the UK and had to report my salary in US$. Average salaries are a lot lower here, even for generally well-paid positions. I'm not in finance or consulting but I'm also not in non-profit, education or charity. My salary would be a tiny fraction of what people in similar roles would report.

If they were really that concerned about the average, they wouldn't take international students

I think compensation matters more if you work for a large corporation (i-bank, PE fund, consulting, F500) where there are clear correlations between certain job titles and salaries. At banks for instance, the analyst and associate base salaries are well known, and adcom knows roughly what the bonus buckets are depending on how well you performed. So if they're looking at 2 bankers from goldman who are both say 1st year associates and one guy got a larger bonus, they could probably assume that he performed better than the other guy. For smaller and more niche firms, even within finance, the picture becomes murkier. At my firm, for example, we don't even have traditional job titles such as "analyst," "associate," "VP," etc. As a matter of fact, it's not uncommon at all for someone to be doing very well and have the same job title for 10 years because of our firm's unique structure.

So my point is, don't stress out too much about this. Adcom knows about this and are not going to hold it against you.

Does every school ask for this information? Do we have an option to opt out?

Yes, all applications ask about this info. However, some schools make mandatory and others not. In big schools which hire third company to verify your profile such as Duke, Columbia, Duke...ans some others. You need to report it honestly as nothing will hurt you.

What is your concern?

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