Volume was especially heavy last week at 131 million shares as the OBV has broken support (line c) that goes back to early 2012.

FORBES: Will Santa Smile On Apple and Amazon?

Volume has been very heavy over the past two weeks and the OBV has broken through major resistance at line d.

FORBES: The Nasdaq 100's Most Overbought

Volume was heavy on the decline, as the longer-term support (line f) was broken.

FORBES: Selling Stampede Shakes Markets

Volume was very heavy on the break, but the OBV gave a good warning as its uptrend (line f) was broken in March.

FORBES: Week Ahead: Fireworks Coming Early?