Just as individuals have their own credit report and rating issued by credit bureaus, bond issuers generally are evaluated by their own set of ratings agencies to assess their creditworthiness. There are 3 main ratings agencies that evaluate the creditworthiness of bonds: Moody's, Standard & Poor's, and Fitch. Their opinions of that creditworthiness—in other words, the issuer's financial ability to make interest payments and repay the loan in full at maturity—is what determines the bond's rating and also affects the yield the issuer must pay to entice investors. Lower-rated bonds generally offer higher yields to compensate investors for the additional risk.
How bond ratings work
Ratings agencies research the financial health of each bond issuer (including issuers of municipal bonds) and assign ratings to the bonds being offered. Each agency has a similar hierarchy to help investors assess that bond's credit quality compared to other bonds. Bonds with a rating of BBB- (on the Standard & Poor's and Fitch scale) or Baa3 (on Moody's) or better are considered "investment-grade." Bonds with lower ratings are considered "speculative" and often referred to as "high-yield" or "junk" bonds.
|Investment grade||Moody's||Standard & Poor's||Fitch|
|Non-investment-grade||Moody's||Standard & Poor's||Fitch|
|Weakest||Moody's||Standard & Poor's||Fitch|
Moody's, Standard & Poor's, and Fitch append their ratings with an indicator to show a bond's ranking within a category. Moody's uses a numerical indicator. For example, A1 is better than A2 (but still not as good as Aa). Standard & Poor's and Fitch use a plus or minus indicator. For example, A+ is better than A, and A is better than A-.
Remember that ratings aren't perfect and can't tell you whether or not your investment will go up or down in value. Before using ratings as one factor in your investment selection process, learn about the methodologies and criteria each ratings agency employs. You might find some methods more useful than others.
Investment grade and high yield bonds
Investors typically group bond ratings into 2 major categories:
- Investment-grade refers to bonds rated Baa3/BBB- or better.
- High-yield (also referred to as "non-investment-grade" or "junk" bonds) pertains to bonds rated Ba1/BB+ and lower.
You need to have a high risk tolerance to invest in high-yield bonds. Because the financial health of an issuer can change—no matter if the issuer is a corporation or a municipality—ratings agencies can downgrade or upgrade a company's rating. It is important to monitor a bond's rating regularly. If a bond is sold before it reaches maturity, any downgrades or upgrades in the bond's rating can affect the price others are willing to pay for it.