1) It’s true that the U.S. has a lower tax burden than most developed countries. It’s also the case that the U.S. is much, much richer than most developed countries, in ways that a casual trip to Paris or London or Stockholm can sometimes obscure. The I.M.F.’s numbers have our purchasing-power-adjusted per capita G.D.P. at $53,101, which is slightly lower than oil-rich Norway (and Luxembourg) but more than $10,000 higher than Sweden and more than $15,000 higher than Denmark; most of the rich European economies are clumped together between the mid-thirties (where you’ll find the French) and the low forties (where you’ll find the Germans). Now: This wealth gap doesn’t necessarily prove anything about the link between low taxes and growth, since the U.S. has basically always been richer and (as Cohn notes) many of the social democracies have grown at a very respectable rate, in per capita terms, over the last few generations. But if you flashed back to the 1970s, you would find a number of very smart people who expected northern Europe (and Japan) to achieve more than respectable growth, and do more than just keep up with U.S. growth: They expected, for plausible theoretical reasons, that we would see continued convergence between the American economy and its developed-world competitors. And that, to put it mildly, did not happen; instead, post-Reagan, the social democracies actually slipped back a bit. So without claiming anything dispositive, I would be much more cautious than Cohn about the claim that growth and tax rates are unrelated, and much, much more hesitant about treating major tax increases as basically a free lunch.