CREDIT rating agencies help to price and assess the risk of debt issued by companies, organisations and governments.
The sector is dominated by three big agencies, Moody’s, Standard & Poor’s and Fitch.
They have courted controversy in recent years, including during the sub-prime crisis when concerns were raised about their accuracy and closeness to companies.
Their ratings range from prime to junk, with an AAA rating only granted to the safest debt, and a C or D rating assigned to debt which is extremely vulnerable to default.
Highly-rated debt tends to be cheaper to issue than lowly-perceived debt, which often pays out high yields.