> But if you allow business expenses to be deducted immediately, that's another path to having a consumption tax with a progressive effective rate curve

If I had written a longer comment, I was going to go in a similar direction. But I think it's a bit fallacious to be talking about that when it would make the tax code even more lopsided to heavily taxing wage earners. Like when you buy a car to be able to get to work, you can't even deduct that from your earnings even though it is a necessary expense for being able to earn that income. If that last part were changed - both with direct deduction of things like living expenses and also unrestricted traditional IRA contributions/withdrawals, then it would make sense to start talking in terms of moving towards a de facto consumption tax. But without doing that, it just seems like a rallying cry to further reduce taxes on the investment-owning classes.

(I'm using the word "deduct" in the business tax sense of direct subtraction, not the personal income tax sense where your expenses have to rise above the level that is otherwise a personal exemption. Being able to deduct so many specific expenses would of course end up placing a heavy bookkeeping burden on individuals, though)