As an addendum to Dave's post below, if you are interested in learning about the current debate/questions surrounding sovereign ratings, have a look at the case of Mexico.
Fitch downgraded Mexico on November 23rd following the Congress' approval of the 2010 budget, which relied too heavily on borrowing and higher oil exports. Mexico's medium-term outlook is under scrutiny, in part, due to the country's over-reliance on a collapsing oil sector (output has declined by about a quarter since 2004, while the sector accounts for almost 40% of state revenue) and failure to sufficiently address the root causes of a widening fiscal deficit, including over-reliance of oil revenues and a small non-oil tax base. JPMorgan has estimated the budget deficit will swell to its widest margin in two decades.
Highlighting the current debate over sovereign ratings, however, is the fact that not everyone agreed with the downgrade. Goldman Sachs' chief Latin American economist Paulo Leme has called the downgrade 'unnecessary roughness' because it overlooks what is still a deficit equivalent to just under 2% of GDP in a recessionary economy. While each country's conditions are different, as a generic measurement a deficit under 4-5% of GDP is widely considered sustainable, especially within the context of a 7.5% annual decline in GDP. I can think of a few countries who would welcome such a small gap. Further, while Leme concedes the Congress could have done far more with the 2010 budget, he feels the downgrade overlooks the value of tax increases included in the bill. The political environment in Mexico is hardly conducive to reform, as Fitch cited as a major factor in its decision, so in this context the tax increases should be viewed as a positive development.
In my opinion, the medium-term concerns centered on the inability of the Calderon government to win Congress' approval for the restructuring of the oil sector are valid, and until this is achieved the country will remain under just scrutiny. But with respect to Mexico's ratings, this assessment places too great an emphasis on medium-term policy considerations, while overlooking the fairly stable near-term profile. Fitch correctly highlights Mexico's vulnerability to future oil-price shocks- relative to its peers Mexico's external debt-to-GDP and debt-to-revenue ratios are high- and limited room for counter-cyclical expansion. But when judged independent of its peers, a downgrade is likely a step too harsh given Mexico's 'healthy banking sector, resilient external accounts, the sovereign's manageable external debt amortization profile, as well as its ability to tap the IMF Flexible Credit Line (FCL) in case of a significant worsening of external financial conditions.' In fact, both the peso and Mexico's bonds rallied following the downgrade, perhaps reflecting a general skepticism amongst market participants.
The case of Mexico illustrates the tricky business of rating sovereign debt and fiscal sustainability, particularly in the post-crisis environment (i.e. widening fiscal deficits amidst tighter borrowing conditions.) While any credit rating agency will tell you that ratings criteria, however objective, are measured within a local context, it seems that in the current environment countries are being painted with rather broad strokes. The spike in CDS spreads for Gulf states following Dubai's announcement is one such example that wholly ignored the unique characteristics of the Dubai situation. The expansionary response of many governments to the crisis has been almost universally credited with averting a total collapse of the global economy. In fact, both the IMF and UN have recently warned against withdrawing this stimulus too soon, lest we manufacture a double-dip recession. While these policies ultimately raise important questions over the medium-term sustainability of imbalances, a clear assessment of a country's ability to exit this response and address larger deficits in the medium-term should control the outlook for a country when, like Mexico, that country is comfortably financing their deficits in the near-term. That picture isn't always clear in the current environment and ratings agencies should thus reserve their judgement until government's are sufficiently confident that growth is sustainable (which they aren't) and have been able to clearly outline their exit strategies (which they haven't.)