The S&P 500® AAA Investment Grade Corporate Bond Index (S&P Rated), a subindex of the S&P 500 Bond Index, seeks to measure the performance of U.S. corporate debt issued by constituents in the S&P 500 rated 'AAA'. The S&P 500 Bond Index is designed to be a corporate-bond counterpart to the S&P 500, which is widely regarded as the best single gauge of large-cap U.S. equities.
https:// us.spindices.com/indices/fixed-income/sp-500-aaa-investment-grade-corporate-bond-index-s-p-rated