The United States ended the 20th century on a roll — for the rich. Between 1973 and 2000, the nation’s most prosperous 1 percent tripled their incomes, after taking inflation into account. The even more prosperous top tenth of that 1 percent did quite a bit better. Their incomes more than quintupled between 1973 and 2000, rising an amazing 414.6 percent. And what about Americans of less exalted means, those stuck in the nation’s bottom 90 percent? Between 1973 and 2000, their incomes rose all of . . . 2.6 percent. Something, in other words, went horribly wrong over the last quarter of the 20th century. And what has happened so far in century 21? Our decision makers in Washington have done their best to make things even worse.