NEW YORK (S&P Global Ratings) Jan. 9, 2017--S&P Global Ratings said today it corrected its fund credit quality rating on the iShares U.S. Preferred Stock ETF by raising it to 'Bf' from 'B-f'. Due to a credit estimation error, we initially rated the fund 'B-f'. The fund volatility rating for the fund remains unchanged at 'S3'. The fund does not limit investment to securities specifically rated by S&P Global Ratings or other nationally recognized statistical rating organizations. At the time of the initial rating on Oct. 20, 2016, over 14% of the portfolio either did not carry a preferred stock rating or the issuer was not rated at all. These exposures were therefore subject to credit estimation for the purposes