[PaulDavisThe1st]

Pareto optimality would be ideal, but across an entire economy, that's almost impossible to measure.

In reality, there is no objective definition of "a fair share", there is only the intent expressed in the tax code (and people of course argue over what the intent "really is"). If people and/or corps. are paying taxes following that intent, then for all practical purposes, they are paying their "fair share".

[csoups14]

A realistic fair share is probably some colloquial measure of people and corporations being equally angry about their taxes and equally angry about others not paying their fair share. It's my personal opinion that corporations have it way too good in the current system, specifically because they've spent millions to find ways to save billions, which people cannot reasonably do, and because they've also spent millions buying our political processes off to ensure tax laws don't meaningfully change.

[PaulDavisThe1st]

Yes, and in fact the entire purpose of a progressive marginal tax system is that "everyone feels the pain of taxation" equally. It recognizes that a fixed percentage, even with a threshold, feels very different if you earn poverty-level wages than if you earn 10000 times that.

And that's what our tax system is designed around.

Corporations, and specifically their status (or otherwise) as "persons" complicates the picture quite a bit.