S&P500 - Price vs Volume - September 2011 to November 2015

Given that the so-called Black Monday of 2011-08-08 (where the markets responded to a downgrade of the US long term credit rating by Standard and Poors) is an extreme event, and arguably marks the next phase of the market, there is some sense in looking at the quality of the market there after.

Volume evaporates on at least two occasions around the current maximums, suggesting that barring further external intervention, we may have reached genuine peak. On the other hand, volume spikes at the support level...