In a way it will be puzzling if the S&P downgrade–despite all the blather about its historic significance–changes anything at all. Certainly, the news should not have come as a surprise: the agency has been talking about it for weeks and the rating for US government debt had been under formal negative review before the announcement. If there is a surprise, it is mainly that the agency had the nerve to go through with it.
More fundamentally, what new information did the downgrade and the analysis supporting it provide? None. After their performance of the past few years, rating agency analysts have, or should have, little credibility in any case. Reports of the initial $2 trillion misunderstanding in S&P’s examination of the Treasury’s books (they used the wrong CBO baseline) lend a tragicomic note, and run their reputational capital down even further. And all this would be true even if US Treasuries were arcane instruments that few investors could afford to monitor carefully, forcing them to rely on the agencies for lack of anything better. In fact, of course, US Treasuries are the most widely and intensely analyzed obligations on the planet. What does S&P know about them that you and I don’t? The informational content of the downgrade is precisely zero.