That's a great line, "But does it work in theory?" I see it almost as often as that other chestnut: "correlation is not causation."

The largest economic expansion in American history came when marginal rates topped out at 91%

I trust that you are not arguing that 91% marginal tax rates caused the largest economic expansion in American history. At most, you can say that high marginal tax rates do not prevent expansion.

But the marginal tax rate changed from 25% (in 1925) to 63% (1932) to 79% (1936) during the teeth of the Great Depression, showing that high marginal tax rates can coexist with recession as well.

I put very little store in these figures, even when they support my side (e.g. the second-largest recession, after WWII, while the rate was 94%). So many other factors come into play. Besides, the marginal tax rate is not the effective tax rate, since there are so many exemptions and workarounds, legal and otherwise. And expansions and recessions are measured by GDP, surely the worst indicator of economic well-being, except for all the others.

I find it plausible that if "astronomically higher marginal tax rates" have any effect, it will be to discourage the creation of additional wealth. My belief is that the primary engine behind increasing prosperity is the creation of new wealth.

Forget the analysis. Is it debatable that even the poor in the United States are better off today than the poor were in previous decades? Not to mention that many of them are better off than most of the wealthy were in centuries past.

Much is made of the distribution of wealth, e.g., in this video. Much attention is given to that lucky Top 1%. I think we should focus on the bottom 1%. That's where the problems are. And I maintain that when the top earners, 90% of whom started from scratch, generate $700 billion dollars a year, this tends on average to benefit everyone, even if the fat cats do not make malaria eradication a hobby.