The first "trick" in using the calculator is deciding what figure to use as your "income". Yes, assuming you figured your taxes correctly, you could pick a number from there, but would it be AGI, MAGI, gross income, etc. In reality, your actual "income" may be none of those things. To me, a better indicator of yearly "income" would be a combination of how much you spent (as in consumed - not what you added to savings for instance) PLUS the net change (positive or negative) in your net worth. I don't think I could quickly figure that one out, so why bother with the "tool".
What I "spend" right now, is significantly more than my official sources of outside income (pension and DWs SS). But, as far as gummint is concerned, they also look at how much I took from 401(k)/IRAs, etc., etc. And yet, in any year, my spending may or may not be offset by gains in investments. And, how do I figure in the increase in "value" of my delayed SS? Should I count that as income? What figure would I use? etc.
Unless I missed it, the article only alluded to the source of income (from gummint statistics) rather than the practical meaning to us 99 percenters of what income we should use.
I guess it's sort of an interesting concept, but doesn't shed much light IMHO. I know we've discussed "rich" many times and I don't think we've ever settled the question.
Personally, I've always been more interested in net worth than income, still I understand that from a tax perspective (or "fair share" argument) income is the more important factor - so far.