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.