Libertarian Megan McArdle objects to my book by insisting that it's "wildly overblown" to pick on supply-siders, since "they've been rather thin on the ground lately." Matthew Yglesias demolishes her objection, pointing out that these few, wee insignificant supply-siders who claim that tax cuts cause revenues to grow include, among many others, George W. Bush, Dick Cheney, Rudy Giuliani, John McCain, AND most of the leading conservative think-tanks and publications. (Matt did not mention Fred Thompson and Mitt Romney, who also have made this claim.) McArdle makes a few other very weak points. First, she writes, "[Chait] complains about the share of national income going to the very richest, without informing the reader that these figures are calculated pre-tax." The reason I included the growing share of income accruing to the rich was to put the rise of the supply-siders into a broader economic context -- our political system has been hijacked by a group dedicated to lessening the share of taxes paid by the rich just as inequality has skyrocketed. Why should I have used after-tax income? But if I had decided to include that, it would have made the trend seem worse, not better. The average tax rate on the top one percent has fallen over the last thirty years even as their share of income has grown. So this fact proves the opposite of what McArdle suggests. Finally, she asserts that I'm wrong to write that "the Laffer Curve was not, strictly speaking, correct." Let me explain this. The Laffer Curve is a concept that says a 0% tax rate and a 100% tax rate will both produce zero revenue. Therefore it's possible to cut taxes and raise revenue. Most economists agree that this is true in theory, but ridicule the notion (put forth by leading Republicans) that current U.S. tax rates are high enough that tax cuts can raise revenues. I think it's also true, in theory, that some tax rates could be high enough that a rate cut could produce higher revenue. I have not disagreed with that idea anywhere in my book. What I took exception to is the idea that a 100% tax rate would produce zero revenue. I know for a fact that this is false. How could I know that? Because if tax rates were 100% I would still work anyway. Why not? It beats sitting home all day. I wouldn't work as hard, but I'd work. The government would get revenue from me. There, that's above zero. I'm also highly confident that other people would work, too. Not nearly as many as do work, and again not very hard, but work they would. The point here is that the supply-side model, which holds that all human activity takes the form of calculating the marginal return on our work, is wrong. People work for all sorts of reasons other than income -- intellectual stimulation, pride in their craft, feeling productive, etc. --Jonathan Chait