OBV can be used to confirm a price trend, upside breakout or downside break. The chart for Best Buy (BBY) shows three confirming signals as well as confirmation of the price trend. OBV and BBY moved lower in December-January, higher from March to April, lower from May to August and higher from September to October. The trends in OBV matched the trend in BBY.
OBV also confirmed trend reversals in BBY. Notice how BBY broke its downtrend line in late February and OBV confirmed with a resistance breakout in March. BBY broke its uptrend line in late April and OBV confirmed with a support break in early May. BBY broke its downtrend line in early September and OBV confirmed with a trend line break a week later. These coincident signals indicated that positive and negative volume were in harmony with price.
Sometimes OBV moves step-for-step with the underlying security. In this case, OBV is confirming the strength of the underlying trend, be it down or up. The chart for Autozone (AZO) shows prices as a black line and OBV as a pink line. Both moved steadily higher from November 2009 until October 2010. Positive volume remained strong throughout the advance.
On Balance Volume (OBV) is a simple indicator that uses volume and price to measure buying pressure and selling pressure. Buying pressure is evident when positive volume exceeds negative volume and the OBV line rises. Selling pressure is present when negative volume exceeds positive volume and the OBV line falls. Chartists can use OBV to confirm the underlying trend or look for divergences that may foreshadow a price change. As with all indicators, it is important to use OBV in conjunction with other aspects of technical analysis. It is not a standalone indicator. OBV can be combined with basic pattern analysis or to confirm signals from momentum oscillators.