“detect a market top, keep a close eye on the daily S&P 500, NYSE Composite, Dow 30, and Nasdaq Composite as they work their way higher. On one of the days in the uptrend, volume for the market as a whole will increase from the day before, but the index itself will show stalling action (a significantly smaller price increase for the day compared with the prior day’s much larger price increase). I call this “heavy volume without further price progress up.” The average doesn’t have to close down for the day, but in most instances it will, making the distribution (selling) much easier to see, as professional investors liquidate stock. The spread from the average’s daily high to its daily low may in some cases be a little wider than on previous days.”
―
William J. O'Neil,
How to Make Money in Stocks: A Winning System in Good Times and Bad