For weeks now, S&P has been threatening to downgrade US debt if the government did not improve its ability to meet payments. The agency said it would spare the US if the debt ceiling deal included at least $4 trillion in cuts over the next decade. According to the bipartisan Congressional Budget Office, the deal cut less that $2 trillion. Despite a $2 trillion dollar mathematical error that postponed S&P's downgrade announcement Friday, the agency stuck to its guns. Politically, this controversial move was necessary if only to show the public that the agency would make good on its threats. This is especially important when reminded of the role the ratings agencies played leading up to the financial crisis; many highly questionable mortgage backed securities were stamped triple A with little or no due diligence performed.
Despite S&P's claims that politics in Washington threaten the ability of the government to pay its bills, and the historical contextual importance of proving the agency is both comptent and willing to judge financial instruments faithfully, one question remains: what about Fitch and Moody's? How can two of the "big three" ratings agencies believe the US to be triple A worthy and not the third? Judging by their ratings of other nations' debt instruments, it is not accurate to say that S&P is consistently more critical, while the other two are consistently more generous. By and large, the only reasonable explanation I can come up with to account for the lack of consensus amongst the agencies regarding our credit worthiness is the high degree of subjectivity that comes with rating debt. The actual difference between a bond rated triple A and AA+ would be difficult to quantify. Although I cannot prove this theory, it is possible that the complex bureaucratic web that makes up an agency (and the nuanced differences between the makeups of the three agencies) permit different conclusions between them, even if their mathematical models were identical (and we must assume they are not). It will be interesting, if nothing else, to see how the international markets react to this news. All we can do is wait and see.