Sure, but as the prevalence of day trading and even automated trading that buys and sells in short periods of time (which you can tell if you look at the price

Sure, but as the prevalence of day trading and even automated trading that buys and sells in short periods of time (which you can tell if you look at the price movements of a stock in a small, say daily interval and notice repetitive price pattern movements), a lot if not MOST stock trading is entirely NOT based on the expectation of underlying value of the stock. Not everyone has a Warren Buffet or Bogle-like approach to long-term investing of stocks.