If you ask me, Jonathan Chait, a writer I respect, has made an ass of himself in a fight he picked with Veronique de Rugy over taxes and progressivity. She offended him by saying that America's income taxes are more progressive than those of other rich countries. Chait assailed her "completely idiotic" reasoning, called her an "inequality denier", "a ubiquitous right-wing misinformation recirculator" and asked if it was really any wonder he cast insults now and then at such "lesser lights of the intellectual world". (Paul Krugman said he sympathises. With Chait, obviously. The only danger here is in being too forgiving, Krugman advises. Chait may think the de Rugys of this world are only lazy and incompetent, but we know them to be liars as well.)
Just one problem. On the topic in question, De Rugy is right and Chait is wrong.
Income taxes in America are more progressive than in other rich countries--according to an authoritiative official study which, to my knowledge, has not been contradicted. The OECD's report "Growing Unequal", on poverty and inequality in industrial countries, includes a table that provides two measures of income tax progressivity in 2005. This is evidently the source of de Rugy's numbers. Here they are in an excel file. According to one measure, America's income taxes were the most progressive of the 24 countries in the sample, except for Ireland. According to the other, they were the most progressive full stop. (A more recent OECD report, "Divided We Stand", uses different data, a smaller sample of countries and a different measure of progressivity: the results are similar.)