Several studies have attempted to deduce the determinants of sovereign bond ratings. In this study, Extreme Bounds Analysis is applied to approximately 30 factors proposed by the literature in order to assess their robustness with a focus on the relative importance that economic and political variables receive in the shaping of the ratings. We find that policies that constrain the public sector are among the most robust. Variables such as rule of law, openness to economic flows, central bank independence, and market friendly policies are found to be more robustly correlated with the ratings than foreign reserves, fiscal deficit, sovereign bond yields, and economic growth.