I've shown you simple way to figure out what you term as "unknowable." Frankly, you're simply wrong on that issue. If you don't believe me, then how about the Tax Policy Center ? There you can see precisely the burden of Individual Income, Corporate Profit, Payroll, Excise, and Estate/Gift tax borne by each income quintile. It's a little more precise than my "80/20" rule because it looks at individual quintiles ... but even then, for ALL but the top 5%, the so-called "hidden" burden is even LESS than I suggested.
I know what taxes are there; your fear of taxes has you seeing tax monsters under the proverbial bed. That you fear some unseen tax monster eating you alive is not proof of its existence.
You never did answer: Do you have ANY idea how much you paid in Sales Taxes last year?