According to Standard & Poor's (S&P), corporate issuance of new bonds this year is likely to exceed 2012 levels. Corporations around the world issued more than $3 trillion in bonds from January through November 2013.

Much of the growth in borrowing is being driven by companies that are below investment grade. S&P expects global corporate speculative-grade bond issuance—that is, issuance by companies rated BB+ or lower—to account for more than 15 percent of the total issuance this year. Not only that, but S&P projects that this year's corporate speculative-grade bond issuance will exceed $500 billion, which would be a record.

“With relatively few alternatives to improve yield, investors were eager to lend even to entities with lower credit quality,” says Diane Vazza, head of Standard & Poor's Global Fixed Income Research. These investments appear to be fairly sound, even as more companies at the low end of the ratings spectrum were able to issue bonds. S&P reports that only 2.2 percent of speculative-grade corporate borrowers defaulted from November 2012 through October 2013, compared with 2.5 percent for all of 2012.