Line ("A/D Line") is used to measure market breadth, being a
cumulative total of the Advancing/Declining Issues indicator. Breadth
in this case means a market's strength.When more trading stocks
are advancing than declining, the A/D Line moves up otherwise down.
The A/D Line may be a better visual indicator of a markets direction
than more traditional measures (such as the S&P Index, for example),
giving a better visual clue as to the market's trend, and how long
it has been trending. As an indicator used in day trading it is
obviously of little use, as it functions best on a far longer timescale.
Often, divergences between the A/D line and a market signal the
end of a trend - the A/D changing BEFORE the underlying market.
The numeric value of the A/D Line is less important than its slope