...NEW YORK (S&P Global Ratings) Dec. 20, 2018--S&P Global Ratings today said it has taken various actions on its fund credit quality ratings (FCQRs) and fund volatility ratings (FVRs) on 79 iShares fixed-income exchange-traded funds (ETFs). (See the Ratings List.) Following our review of the iShares funds under our FCQR criteria, we raised five ratings, lowered 12, and affirmed 62. In general, FCQR downgrades were largely driven by changes in the constituents of the underlying indices. The components of the underlying indices typically change over time depending on market conditions and issuance trends. The downgrades were not limited to any one sector, but spanned corporate bond, high yield, emerging markets, and preferred shares ETFs. We raised our FCQRs on five iShares iBonds ETFs, which are a collection of bond funds that hold a diversified portfolio of bonds with similar maturity dates and have a final payout in their maturity year. As these term portfolios move toward their expiration...