> Megan McArdle is a hardened libertarian sophist
That's an ad-hominem attack that has nothing to do with the substance of this discussion. How about sticking to the actual numbers?
> 1) With respect to healthcare, investopedia has different numbers than the ones she cites
Let's assume the investopedia numbers are right (though it's not clear why their uncited administrative costs number is more authoritative than an OECD report on administrative costs). They claim 5% of GDP in administrative costs (25% of 20%). The drug numbers they mention as being "saveable" are $11.6 billion per year; that's .0006% of GDP. No other numbers are cited for drugs there. For defensive medicine, .03% of GDP. For the other items, no numbers are given.
So we could potentially spend about 5% of GDP less on healthcare; the other bits all look like rounding error on that. I used $19.39 trillion for the current annual US GDP, fwiw.
And just to be clear, the actual US federal government spending on healthcare is about $1 trillion a year, or maybe 5-6% of GDP, as far as I can tell. The remaining 14-15% of GDP is spent outside the federal budget already. If we're trying to put it in the federal budget that means raising taxes by 9% of GDP or so.
> Eliminate Imperialism - Save > $1T dollars by not fighting wars based on lies.
This would definitely be nice, but that doesn't seem to be what most people propose. Again, the context is people proposing "just tax the 1%".
> Tax the (Natural Person) Rich
Right, this is the thing under discussion: taxing "the 1%". The total income of the top 1% is something around 20% of total personal income according to https://www.epi.org/blog/top-1-percent-receive-record-high-s... and total personal income is around $16.5 trillion according to https://www.statista.com/statistics/216756/us-personal-incom...
So if we taxed away every single penny "the 1%" earn, that gives us 16% of GDP. That's assuming that there are no disincentive effects, emigration, etc, etc. Probably a bad assumption.
> Eliminate the Rentier Class
I'm not sure what your actual proposal is here, but at this point I suspect we're way outside the realm of the politically feasible or desirable. That said, can you quantify this, please?
> Tax the Tax Evaders
I would be very much behind this idea. Again, this is not the same as "just tax the 1%".
Anyway, last I checked US government spending (including all levels of government) was about 37% of GDP. If we add the very optimistic 16% we can get by taxing "the 1%" we get to 53%. That's still less than France or Finland or Denmark spend. Yes, we could nationalize healthcare if we did that, fairly easily. We couldn't do all the other things people want to do by "taxing the 1%".
I agree that if we radically restructured everything about how the government is funded and what we spend money on then there are a lot more options. But, again, what people tend to propose is "just tax the 1% and use that money for X, Y, and Z". And there's not enough money in that bucket to do all those things.