Whether markets are green or red at the end of the day often masks their internal health. Bear markets can maul prices down on any volume, but bull markets need buying pressure to keep them going. Think of shooting water from your garden hose up into the sky, it can only stay up as long as the pressure compels it. After that the water necessarily must fall back to earth. One of the more enlightening indicators of market health is the Lowry's index of buying versus selling pressure. Paul Desmond, President of Lowry Research, was recently featured on CNBC's "Fast Money Final Call," discussing why the data is suggesting a more substantial correction may be still to come.