According to this WSJ article, the difference in the yield between junk bonds and Treasuries with similar maturities is at its smallest (about 1.3%) since the credit crisis.
There are plenty of reasons why this is the case. As investors struggle to find income and the corporate earnings picture continues to improve, taking the plunge in higher risk debt isn't as scary as it used to be. But as I've said in previous posts, it is likely that such spread compression will drive market participants to other places.