Advance-Decline Line (A/D Line)

Is the cumulative running total of the plurality of advancing over declining issues for a given period, usually a day. It is used as a proxy for the broad market or the price of the average share. When the market, as measured by the DJIA or S&P Composite makes a new high and this is not confirmed by the A/D Line this is known as a negative divergence. Negative divergences are interpreted as a bearish sign.  Positive divergences develop at market bottoms when the A/D line fails to confirm a new low in the averages. These are regarded as bullish signs. Generally speaking the longer the divergences the more important the signal. Some A/D lines, such as the AMEX, OTC and that in Japan appear to have a permanent downward bias and should only be used for very short-term analysis over a period of a few weeks.