Credit Rating Breakdown: AAA

AAA bonds carry the highest credit-quality rating as assigned by Standard & Poor's or Moody's. The range of ratings includes AAA, AA, A, BBB, BB, B, Below B and Not Rated. For the purpose of Morningstar's calculations, US government bonds are considered AAA.  For municipal bonds, anything at or below BBB is considered a high-yield or junk bond. Nonrated municipal bonds generally are classified as BBB. Other nonrated bonds generally are considered B.