Classifying investment instruments according to their quality has long been a tradition of the bond market. A ratings system is used to help determine creditworthiness of a borrower. This makes the corporate and public sector bond market easily adapted into the paradigm of Quality Investing. Bonds are separated into two types: investment grade and junk bonds.
With investment grade bonds, a credit rating is determined by different companies. If the bond is rated BBB- or higher by Standard and Poor's, Baa3 or higher by Moody's or BBB(low) or higher by the Dominion Bond Rating Service, it is considered a Quality Investment. Anything else is considered a speculative grade investment or junk bond.