What is the Absolute Breadth Index?

Absolute Breadth Index (ABI) is an indicator to measure the market volatility without factoring in price direction. It is a momentum indicator which tracks the movement of the stocks on the exchange but not their directions. The absolute breadth index is the absolute value of the difference between the number of advancing stocks and number of declining stocks. Regardless of whether more stocks are advancing, or more are declining, the difference is always an absolute number. The Absolute Breadth Index is calculated as- ABI = Absolute Value [(Number of Advancing Stocks) (Number of Declining Stocks)]

How is the Absolute Breadth Index Used?

The absolute breadth index was developed by Norman G Fosback. He discussed the concept in his book Stock Market Logic. The calculation if absolute breadth index is based only on advancing and declining values; thus, it is classified as a breadth indicator. Traditionally, advance/decline based technical indicators were calculated using the New York Stock Exchange (NYSE) as the standard. However, any exchange or subset of an exchange can be used for calculating the absolute breadth index. The absolute breadth index measures how investors feel about buying or selling stocks, thus it is known as sentiment indicator. When the absolute breadth is low, that means the advancing and declining issues are mostly in balance, so the overall market is likely to be stable. A high absolute breadth indicates that the issues are either advancing or declining, so the market is volatile. Norman Fosback argued, a very high absolute breadth index value is more likely to lead to an eventual rise in the prices of the stocks that are being analyzed. Whereas a very low value indicates towards a decline in the stock price in the near future. This index is used for determining when the market is most volatile. Long-term investors use this index to estimate, when a market is in sustainable bull or bear market. In his book Fosback showed, if the ABI reading for the 10-week moving average is 40 percent that indicates the market is bullish and if the reading is below 15 percent, it indicates towards bear market. But, as now, the number of stocks traded on the New York Stock Exchange is much higher, these hard numbers are no longer a valid indicator of primary trends. However, the absolute breadth index is not a standard way to measure the market volatility. The traditional way of measuring the market volatility is to assess price change or price trading range within a specific time period. The absolute breadth index does not consider how much a stock is moving, it just measures whether a stock is advancing or declining in respect to the prior days closing price. So, this index may not always be a reliable indicator of market volatility. As absolute breadth index is calculated on the basis of the advance decline data, which are derived from the previous trading sessions close, the absolute breadth index is more useful for analyzing longer term trends. Using absolute breadth index in intraday technical analysis may not provide an accurate reading.