NEW YORK (Standard&Poor's CreditWire) Dec. 21, 2000--Standard&Poor's today affirmed its single-'A'-plus counterparty credit and financial strength ratings on Noridian Mutual Insurance Co. (d/b/a Blue Cross and Blue Shield of North Dakota) (Noridian Mutual). The outlook is stable. The rating reflects Noridian Mutual's dominant market position, strong capitalization, and conservative investment practices, offset by marginal, though improving, earnings performance, regulatory restrictions on capital accumulation and rate increases, and a potentially more competitive market environment. Major rating factors: -- Dominant market position. Noridian Mutual is the leading health insurer in North Dakota, with an estimated 78% market share, based on total insured premiums in the state. This has been achieved through a strong customer focus, the development of