Los argumentos de S&P

En Standard & Poor´s, las razones para bajar la deuda americana de AAA  a AA+, con posible revisión negativa.

Compared with previous projections, our revised base case scenario now assumes that the 2001 and 2003 tax cuts, due to expire by the end of 2012, remain in place. We have changed our assum-ption on this because the majority of Republicans in Congress continue to resist any measure that would raise revenues, a position we believe Congress reinforced by passing the act. Key 
macroeconomic assumptions in the base case scenario include trend real GDP growth of 3% and consumer price inflation near 2% annually over the decade. Our revised upside scenario--which, other things being equal, we view as consistent with the outlook on the 'AA+' long-term rating being revised to stable--retains these same macroeconomic assumptions. In addition, it incorporates $950 billion of new revenues on the assumption that the 2001 and 2003 tax cuts for high earners lapse from 2013 onwards, as the Administration is advocating. In this scenario, we project that the net general government debt would rise from an estimated 74% of GDP by the end of 2011 to 77% in 2015 and to 78% by 2021. 

Es decir, el mejor escenario  prevé una deuda del 78% del PIB en 2021.

Our revised downside scenario--which, other things being equal, we view as being consistent with a possible further downgrade to a 'AA' long-term rating--features less-favorable macroeconomic assumptions, as outlined below and also assumes that the second round of spending cuts (at least $1.2 trillion) that the act calls for does not occur. This scenario also assumes 
somewhat higher nominal interest rates for U.S. Treasuries. We still believe that the role of the U.S. dollar as the key reserve currency confers a government funding advantage, one that could change only slowly over time, and that Fed policy might lean toward continued loose monetary policy at a time of fiscal tightening. Nonetheless, it is possible that interest rates could rise if investors re-price relative risks. As a result, our alternate scenario factors in a 50 basis point (bp)-75 bp rise in 10-year bond yields relative to the base and upside cases from 2013 onwards. In this scenario, we project the net public debt burden would rise from 74% of GDP in 2011 to 90% in 2015 and 
to 101% by 2021.

El escenario más negativo prevé una deuda del 101% del PIB  en 2021, debido a un posible aumento de los tipos de interés previstos en el escenario mejor.
S&P justifica que otros países con peores cifras, como Francia, se mantengan en AAA mientras EEUU es rebajada.

When comparing the U.S. to sovereigns with 'AAA' long-term ratings that we view as relevant peers--Canada, France, Germany, and the U.K.--we also observe, based on our base case scenarios for each, that the trajectory of the U.S.'s net public debt is diverging from the others. Including the U.S., we estimate that these five sovereigns will have net general government debt to 
GDP ratios this year ranging from 34% (Canada) to 80% (the U.K.), with the U.S. debt burden at 74%. By 2015, we project that their net public debt to GDP ratios will range between 30% (lowest, Canada) and 83% (highest, France), with the U.S. debt burden at 79%. However, in contrast with the U.S., we project 
that the net public debt burdens of these other sovereigns will begin to decline, either before or by 2015.

Ha aparecido una discrepancia entre el Tesoro y la agencia de 2 billones de euros en gastos en 10 años que afectan significativamente  a los resultados. Sin embargo, S&P no ha rectificado, basándose en la mala disposición institucional para controlar el déficit. esto parece una censura encubierta a la negativa de los REP a subir los impuestos.
En todo caso, de aceptar ese recorte de 2 billones, la deuda al cabo de 10 años sería del 75%, frente al 101%.
¿Tiene algún rigor esto, o es "demasiado riguroso"?
Warren Buffet dice que no tiene nada de sentido.

“Think about it. The U.S., to my knowledge owes no money in currency other than the U.S. dollar, which it can print at will. Now if you’re talking about inflation, that’s a different question.”

 Krugman lo critica acerbamente, basándose en la insignificancia de los tipos de interés:

Start with interest rates. What matters for debt sustainability is the real interest rate, since what matters is keeping real debt, not nominal debt, from growing. (World War II debt never got paid off, it just eroded in real terms to the point where it was trivial). As of yesterday, the US government could lock in 30-year bonds at a real interest rate of 1.25%. That means that a trillion dollars in extra debt would mean $12.5 billion a year in additional real interest payments.

Meanwhile, the CBO estimates potential real GDP in 2021 at about $18 trillion in 2005 dollars, or around $19 trillion in 2011 dollars.

Put these together, and they say that an extra trillion in borrowing adds something like 0.07% of GDP in future debt service costs. Yes, that zero belongs there. The $4 trillion S&P said it needed to see clocks in at less than 0.3% of GDP.

 So this is an outrage — not because America is A-OK, but because these people are in no position to pass judgment.