Jun 08 2019 Off BBB Debt by Sector in the U.S. By sector in the U.S., financial institutions have the largest amount of ‘BBB’ debt: $744 billion. That’s 53% of investment-grade bonds in the United States.You may also like “The U.S. Corporate Bond Debt Rated ‘BBB’ Exceeds $3 trillion.” Image: S&P Global Fixed Income Research