However, in the short-term this metric is also of some value - please, look at the chart below:
The chart shows that every time the spread between junk bond and 10-year treasuries starts to widen (the downtrend is renewed) the broad equity market, represented by S&P 500, follows it (starts to go down a little bit later).
Since mid-March the spread has been widening so, if my thesis is correct, the broad equity market should start its leg-down soon.
Another thing - as the chart below shows, the last S&P 500 strong increase was made at decreasing volume (yellow area):
Since the middle of February 2016 the index went up 12% but the average daily volume went down from 3.5 billion shares to 2.3 billion shares (a decrease of 34%). It is by no means a bullish pattern...