NY -- Standard&Poor's CreditWire 5/13/98 –- Standard&Poor's today assigned its double-'A'-minus rating to Portage, Mich.'s transportation fund bonds series 1998A dated May 1, 1998 due Dec. 1, 2018. The bonds are scheduled to sell May 19, 1998. At the same time, Standard&Poor's affirmed its double-'A'-minus rating on Portage's outstanding G.O. debt and the building authority's debt issued for the city, which combined total $38 million. The rating reflects the following strengths: -- A diverse economic base, -- Above-average income levels, and -- A solid financial position. Offsetting factors include a limited tax pledge, some economic concentration, and high carrying charges. Portage is located midway between Chicago, Ill. and Detroit, Mich. Pharmacia&Upjohn Inc.,
