A study conducted by Standard and Poor's Global Fixed Income Research estimated the size and structure of the US corporate debt market. It found that companies that have investment grades of BBB- and higher had accounted for 67% of US corporate debt.

On the other hand, it found that nonfinancial issues comprised 70% of rated debt outstaind. These facts were contained in an article published by Standard & Poor's Global Fixed Income Research entitled, "Analyzing the Size and Structire of the US Investment Grade and Speculative-Grade Corporate Debt Market in 2013."

According to the Head of Standard & Poor's Global Fixed Income Research, "By issuer count, the 'B' rating category is the largest in the US (with 34% of issuers in the 'B' category), through these companies tend to be much smaller on average then their investment grade counterparts."

The sample consisted of US corporate instruments amounting to US$6.59 trillion as of March 31, 2013. As for sectoral representation, financial institutions topped the list with 24% of total debt, with utilities at 9% and telecommunications at 8%.