Related: The King of Junk Bond ETFs

Corporate debt is reaching its highest level since before the financial crisis, which has caused Moody’s to warn that substantial trouble is ahead for junk bonds when the next downturn arrives.

The ratings agency said the ongoing low-rate environment and investor appetite for yield have pushed companies to issue huge amounts of debt that provide low levels of protection for investors, CNBC reports. However, default rates are still low, at least for now.

Over 86% of JNK’s holdings are rated BB or B, but over 13% carry the speculative CCC rating as well. JNK compensates investors for the risk with a 30-day SEC yield of 6.17%.

For more information on the fixed-income space, visit our bond ETFs category.