Volume(V) and open interest (OI) are very important when analyzing markets and working out how much 'momentum' is behind any given a price movements.
For example, it is a generally accepted tenet of TA that for a price movement in either direction to be confirmed you will see a corresponding increase in market volume/turnover in the particular stock/index being analyzed. When looking at futures markets OI also comes into the equation and changes in price trends tend to show up first in the OI figures. These measures of interest in a market are closely watched by the pros and tend to be ignored by private investors. If you are aware of how they can affect price movements you can move to exploit them ahead of the army of private investors, who, through ignorance miss out on many of the moves in which professional investors make good market returns.
As well as looking at the established rules for interpreting V/OI changes and their likely effect on subsequent price action, we also look at the caveats surrounding their use.