NEW YORK (S&P Global Ratings) Dec. 20, 2018--S&P Global Ratings today said it assigned the following fund credit quality ratings (FCQRs) and fund volatility ratings (FVRs) on four new iShares fixed-income exchange-traded funds (ETFs): 'Af/S2' ratings on the iShares Global Green Bond ETF, 'AA-f/S2' ratings on the iShares ESG U.S. Aggregate Bond ETF, 'AA-f/S3' ratings on the iShares iBonds Dec 2025 Term Muni Bond ETF, and 'BBBf/S3' ratings on the iShares iBonds Dec 2028 Term Corporate ETF. The iShares Global Green Bond ETF (BGRN) seeks to track the investment results of Bloomberg Barclays MSCI Global Green Bond Select (USD Hedged) Index, while mitigating exposure to currency fluctuations versus the U.S. dollar. BGRN targets exposure to investment-grade global green bonds where