In the United States , NOTES or BONDS issued by governmentsponsored or governmentguaranteed institutions (e.g., FEDERAL NATIONAL MORTGAGE ASSOCIATION , GOVERNMENT NATIONAL MORTGAGE ASSOCIATION, FEDERAL HOME LOAN MORTGAGE CORPORATION ). The securities carry explicit or implicit government support related to PRINCIPAL and interest payments, and thus carry the strongest CREDIT RATINGS. Agency securities, which are issued with short to longterm maturities and fixed or floating coupons, are exempt from REGISTRATION requirements established by the SECURITIES AND EXCHANGE COMMISSION .