A rating is the assessment of the creditworthiness of a company or country by specialised credit rating agencies (CRAs). The most well-known CRAs are Standard & Poor’s (S&P), Moody’s and Fitch Ratings.
A credit rating is usually expressed by letters and is intended to provide creditors and bond buyers with an appraisal of the likelihood that interest payments will be made and the capital be repaid. It is regularly renewed and, where necessary, adjusted.
In the case of S&P, the best possible credit rating is an AAA, which may subsequently be downgraded to AA, A, BBB, BB, B, CCC, CC, C and lastly D. Ratings of AAA up to BBB are considered investment grade, below which many institutional investors are not allowed to purchase. A company or country with a rating of BB or lower is considered speculative. They are called non-investment grade or high-yield.