HYG and JNK, the junk ETFs, are paying 30-day SEC yields of more than 5% while yields on 10-year Treasury notes are hovering around 1.8%.

According to fixed-income portfolio manager David Schawel, the spread between junk-bond yields and the S&P 500 earnings yield recently turned negative for the first time ever, “showing just how much the yields on high-risk bonds have come down as central banks keep benchmark borrowing rates depressed and investors search further out on the risk spectrum for yield.”

“Even as credit quality deteriorated, Fed efforts to push investors into riskier assets drove unprecedented amounts of cash into the corporate debt market, fueling the biggest gains since 2009,” Bloomberg reports.

However, after such a strong run, some traders are using high-yield bond ETF options to speculate on a pullback or hedge existing positions. [Junk Bond ETF Yielding Over 6% Sees Record Bearish Bets]

“If you look at some of the spreads where these corporates are trading, you start to wonder how much more of a rally can you get?” Kenneth Naehu, portfolio manager at Bel Air Investment Advisors, told Bloomberg. “That doesn’t mean it’s impossible, you’re just up against levels that will be difficult to rally from.”

Full disclosure: Tom Lydon’s clients own HYG, JNK and LQD.