Joseph Granville - On-balance volume

On-balance volume (OBV) is a technical analysis indicator intended to relate price and volume in the stock market. OBV is based on a cumulative total volume.

Total volume for each day is assigned a positive or negative value depending on prices being higher or lower that day. A higher close results in the volume for that day to get a positive value, while a lower close results in negative value. So, when prices are going up, OBV should be going up too, and when prices make a new rally high, then OBV should too. If OBV fails to go past its previous rally high, then this is a negative divergence, suggesting a weak move.

The technique, originally called "cumulative volume" by Woods and Vignolia, was later named in 1946, "on-balance volume" by Joseph Granville who popularized the technique in his 1963 book Granville's New Key to Stock Market Profits[1]. The index can be applied to stocks individually based upon their daily up or down close, or to the market as a whole, using breadth of market data, i.e. the advance/decline ratio.

OBV is generally used to confirm price moves.[4] The idea is that volume is higher on days where the price move is in the dominant direction, for example in a strong uptrend more volume on up days than down days.

Info Source http://en.wikipedia.org/wiki/On-balance_volume