Declining volume at new highs can often lead to short-term difficulties.  Below is a study related to SPY and SPY volume that I’ve shown a few times in the Subscriber Letter.  It popped up in the Quantifinder again on Thursday.

This appears to suggest a mild downside edge.  The high probability of some kind of decline despite the fact that it always occurs in an intermediate-term uptrend makes the study compelling enough to me to take under consideration.