Accumulation/Distribution Line
The Accumulation/Distribution Line (A/D Line) is a volume-based technical indicator developed by Marc Chaikin that attempts to assess whether a security is being accumulated (bought) or distributed (sold) by relating the closing price's position within the day's high-low range to the period's volume. It is one of the foundational volume-price indicators in the technical analysis literature.
The Accumulation/Distribution Line was developed by Marc Chaikin as an improvement over On-Balance Volume (OBV), another volume-based indicator created by Joe Granville. Where OBV assigns the full day's volume to either buying or selling depending solely on whether the close was up or down, the A/D Line uses the Close Location Value (CLV) to weight the volume contribution by where the close fell within the high-low range. A close at the very top of the day's range results in the full volume being attributed to accumulation; a close at the very bottom attributes the full volume to distribution; a close exactly in the middle contributes zero.
The cumulative running total of these weighted volume values produces the A/D Line. Over historical periods in U.S. equity markets, technical analysts have observed patterns in how the A/D Line's direction corresponded to the underlying stock's price trend. Periods where the price was rising but the A/D Line was declining were noted in the historical literature as instances of divergence, which analysts observed sometimes preceded price reversals in historical data sets. These observations are descriptive of historical patterns and do not constitute forward-looking predictions.
The A/D Line is available on major U.S. charting platforms and is a component of several composite technical systems. It forms the basis of the Chaikin Money Flow indicator (a windowed version of the same calculation), and its conceptual framework influenced subsequent volume-price indicators developed by later market technicians. The CMT Association, which administers the Chartered Market Technician credential in the United States, includes volume-price indicators including the A/D Line in its educational curriculum.
Interpreting the A/D Line requires understanding that it is a cumulative indicator, meaning its absolute level is less meaningful than its directional trend relative to price. Its construction is based entirely on historical price and volume data for the security being analyzed.
One limitation of the A/D Line worth noting is that it uses only the closing price and the day's range in its CLV calculation, ignoring intraday price action between the open and the close. A stock that gaps down at the open, trades lower throughout the day, but rallies strongly in the final hour to close near the high will register a positive CLV for that day despite the adverse price action for most of the session. This characteristic means the A/D Line can present a more favorable historical volume-price picture than intraday data might suggest, which is one reason practitioners sometimes supplement it with other volume and price indicators when constructing a multi-factor technical view.