A credit rating is designed to measure an obligee's ability to repay principal to an obligor in the future. Moody's has 9 ratings from Aaa to C, while S&P has 10 ratings from AAA to D. Among the ratings, Moody's considers grades Aaa to Baa as investment grades, and the grade Ba and lower are considered to be the non-investment grade, while, under the S&P standards, AAA to BBB are considered as investment grades, whereas BB or lower is considered as non-investment grade. Even after a credit rating is given, credit rating agencies continuously observe companies subject to rating, adjust the rating from time to time and present future prospects. If the current rating is likely to rise in the future, a “positive” sign is added to the rating, while if the rating is likely to stay unaltered and to fall, “stable” and “negative” signs will, respectively, be attached to the end of each rating.