This chart compares the price performance of the S&P 500 Index to that of the iShares iBoxx High Yield Corporate Bond Fund (HYG). Both were tracking pretty closely until recently, but then the prices of corporate bonds started to soar while equity indices languished. I think this another one of those cases where the bond market is leading the way for the equity market. First, we had swap spreads decline. Now, we are seeing spreads on corporate bonds decline. Eventually we will see equity prices picking up.
Full disclosure: I am long HYG and IVV at the time of writing.