The analysis of volume is a basic yet very important element of technical analysis.
Volume provides clues as to the intensity of a given price move.
Low volume also often occurs during the indecisive period during market bottoms. High volume levels are characteristic of market tops when there is a strong consensus that prices will move higher. Just before market bottoms, volume will often increase due to panic-driven selling. Volume can help determine the health of an existing trend. The following chart shows Merck and its volume.