It is often said a picture paints a thousand words; in the case of this chart, it paints more. Day in and day out, there is one inimitable indicator that if looked at will tell you everything you need to know about the day's market performance - volume. The last few weeks - post-Draghi, Post-Knight, stunned many with just how low volume can get; and implicitly just how much the battle-bots remain in charge. Clarifying this picture of low volume strength and high volume weakness, John Lohman has created the following chart - summarized thus: YTD, low volume days have seen the S&P 500 rise around 15% in aggregate, while high volume days have seen the S&P lose around 5% in aggregate. The linear nature of the low-volume move is simply remarkable - perhaps September will bring some real volume back, and now we know what that means for market direction.