Advance-Decline (A/D) Line

The cumulative sum of the difference between the number of issues advancing versus the number of issues declining in a particular stock market index that day

What is the Advance-Decline (A/D) Line?

The Advance-Decline (A/D) line is an indicator that is utilized by investors who want to measure the number of individual stocks. The A/D line can determine whether the stocks are participating in either a market fall or market rise.

 

Advance-Decline (A/D) Line
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Summary

  • The advance-decline (A/D) line functions as a stock market technical indicator.
  • It can help understand individual stock change and market performance.
  • The A/D line is calculated by subtracting the current day’s declining stocks from the current day’s advancing stock then adding yesterday’s A/D line value.

 

Understanding Advance-Decline (A/D) Lines

To be explained further, the A/D line is a plotting of the cumulative sum of the difference between the number of issues advancing versus the number of issues declining in a particular stock market index that day. Once the differences are calculated, they are plotted, and the index will either move up if they are advancing or move down when declining.

Stocks are defined as an advancing stock if they are being traded above the previous trading session’s closing price. On the other hand, a stock is considered declining stock if they are trading below the previous day’s closing price.

When prices of large stocks change, they may result in a disproportionate effect on stock market indices, such as the S&P 500 or NASDAQ Composite Index. The stock indices, in particular, are market capitalization-weighted stock market indices. They represent a grouping of stocks; therefore, the indicator would become helpful in understanding how the market movement of rising or falling is affecting individual stocks and, even more specifically, smaller stocks. It is the case because it will give equal weight to both small and large companies in a market capitalization-weighted scenario.

Overall, the benefit to the A/D Line is that it will provide information regarding the performance of individual stocks on a particular day. The A/D line is based on the Advance-Decline data and is one of the most popular indicators.

Otherwise known as A/D Data, Advance-Decline data is calculated to demonstrate the number of advancing and declining stocks in addition to the traded volume that is associated with the individual stocks within a specific market index or stock market exchange. Overall, the data measurement will display market breadth.

 

How to Calculate the Advance-Decline Line

Calculating the Advance/Decline line involves subtracting the current day’s declining stocks from the current day’s advancing stock then adding yesterday’s A/D line value.

 

Current Day’s Advancing Stock – Current Day’s Declining Stocks + Previous Day’s A/D Line Value

 

Importance of the Advance-Decline Line

The advance-decline line is important for a multitude of reasons. Firstly, it helps current and prospective investors in judging and analyzing the overall performance of the market. It is done because the A/D line will demonstrate the movement of the indexes by analyzing the stocks on an individual level. Therefore, it is important to understand and utilize the A/D line so that, as an investor, you can see a truer view of the market’s situation.

Additionally, it is important because it can aid in providing a daily overview of trades, which is vital for investors. Finally, the A/D line is important because it can reveal divergence in the market, as it has done previously in history.

 

Divergence

Divergence is used to describe a situation when the stock market moves in the opposite direction of the advance-decline line. Interestingly, if the situation occurs, it tells you that the index may not be portraying the correct direction of the overall market.

 

Example

An example of divergence between the A/D line and the stock market index happened in March 2008 before the market collapse. Additionally, there is another example of divergence near the end of the dot-com bubble between 1999 and 2000.

The dot-com bubble was during a time where there was a large amount of speculation regarding a large internet-based growth period. More specifically, the NASDAQ Composite Index spiked then fell extremely low because of the dot-com bubble. It demonstrated divergence in the market.

 

Additional Resources

CFI is the official provider of the Certified Banking & Credit Analyst (CBCA)™ certification program, designed to transform anyone into a world-class financial analyst.

To keep learning and developing your knowledge of financial analysis, we highly recommend the additional resources below:

  • Advanced Technical Analysis
  • ARMS Index
  • McClellan Oscillator
  • Speed Lines

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