A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations, including specific securities, money market instruments or other debts. Ratings are subject to change without notice. Short-term credit ratings are measured on scale that generally ranges from A-1 (highest) to D (lowest) for Standard & Poor's and from P-1 (highest) to NP (lowest) for Moody's and F1+ (highest) and D (lowest). S&P and Fitch ratings will also denote those securities that possess extremely strong safety characteristics with a plus sign (+) designation. NR or blank fields indicated the debtor was not rated, and should not be interpreted as indicating low quality.