Technical Indicator - On Balance Volume (OBV)

Technicians have experimented with many volume indicators to help quantify buying or selling pressure. Trying to "eyeball" the vertical volume bars along the bottom of the chart is not always precise enough to detect significant shifts in the volume flow. The simplest and best known of these volume indicators is on balance volume or OBV. Developed and popularized by Joseph Granville in 1963, Granville's New Key to Stock Market Profits, OBV actually produces a curving line on the price chart. This line can be used either to confirm the quality of the current price trend or warn of an impending reversal by diverging from the price action.

The price chart with the OBV line along the bottom of the chart instead of the volume bars. Notice how much easier it is to follow the volume trend with the OBV line.

The construction of the OBV line is simplicity itself. The total volume for each day is assigned a plus or minus value depending on whether prices close higher or lower for that day. A higher close causes the volume for that day to be given a plus value, while a lower close counts for negative volume. A running cumulative total is then maintained by adding or subtracting each day's volume based on the direction of the market close.

It is the direction of the OBV line (its trend) that is important and not the actual numbers themselves. The actual OBV values will differ depending on how far back you are charting. Let the computer handle the calculations. Concentrate on the direction of the OBV line.

The on balance volume line should follow in the same direction as the price trend. If prices show a series of higher peaks and troughs (an uptrend), the OBV line should do the same. If prices are trending lower, so should the OBV line. It's when the volume line fails to move in the same direction as prices that a divergence exists and warns of a possible trend reversal.