Advancing, declining, and unchanged volume are all
market momentum indicators. They reflect movement on the New York Stock
exchange in millions of shares.
Advancing volume is the total volume for all
securities that advanced in price. Declining volume is the total volume
for all securities that declined in price. And similarly, unchanged
volume is the total volume for all securities that were unchanged in
price.
Interpretation
Numerous indicators have been developed using up and
down volume indicators. These indicators include the Cumulative Volume
Index, Negative Volume Index, Positive Volume Index, and the
Upside-Downside Ratio. Charts of the advancing or declining volume can
be used to look for volume divergences (where advancing volume increases
but the market falls) to see if selling pressure is waning, to view
daily trends, etc.
Due to the erratic fluctuations in advancing and
declining volume, I suggest you smooth the indicators with a 3- to
10-day moving average.
Example
The following chart shows the S&P 500 and a 10-day
moving average of advancing volume.
A bearish divergence developed as prices tried to
rally (trendline "A") while the advancing volume was declining (trendline
"B"). If you only looked at the S&P 500 you might think the market was
gaining strength. The Advancing Volume showed the true picture and
prices were forced to correct.