S.& P. gave Lehman Brothers, whose collapse triggered a global panic, an A rating right up to the month of its demise. And how did the rating agency react after this A-rated firm went bankrupt? By issuing a report denying that it had done anything wrong. So these people are now pronouncing on the creditworthiness of the United States of America? Wait, it gets better. Before downgrading U.S. debt, S.& P. sent a preliminary draft of its press release to the U.S. Treasury. Officials there quickly spotted a $2 trillion error in S.& P.’s calculations. And the error was the kind of thing any budget expert should have gotten right. After discussion, S.& P. conceded that it was wrong — and downgraded America anyway, after removing some of the economic analysis from its report.