...Standard & Poor's Ratings Services assigned its '###' long-term rating to Polk County, Iowa's series 2016 taxable general obligation (GO) refunding bonds. At the same time, Standard & Poor's affirmed its '###' long-term rating on the county's existing debt. The outlook is stable. The county's full-faith and credit pledge, and an agreement to levy ad valorem property taxes without limitation on the rate or amount, secure the debt. The series 2016 bond proceeds will be used to refund the county's outstanding debt, including that of series 2010A, series 2010B, series 2012B, and a portion of the June 1, 2016 maturity of the GO bonds series 2015A, to save on interest cost. Polk County's bonds are eligible to be rated above the sovereign because we believe the county can maintain better credit characteristics than the U.S. in a stress scenario. Under our criteria, U.S. state and local governments are considered to have moderate sensitivity to country risk. (For more information, see "Ratings...