Excellent quote from Graham and Dodd’s famous text Security Analysis.
“Undervaluations caused by neglect or prejudice may persist for an inconveniently long time, and the same applies to inflated prices caused by overenthusiasm or artificial stimulants. The particular danger to the analyst is that, because of such delay, new determining factors may supervene before the market price adjusts itself to the value as he found it. In other words, by the time the price finally does reflect the value, this value may have changed considerably and the facts and reasoning on which his decision was based may no longer be applicable.
The Relationship of Intrinsic Value to Market Price. The general question of the relation of intrinsic value to the market quotation may be made clearer by the following chart, which traces the various steps culminating in the market price. It will be evident from the chart that the influence of what we call analytical factors over the market price is both partial and indirect—partial, because it frequently competes with purely speculative factors which influence the price in the opposite direction; and indirect, because it acts through the intermediary of people’s sentiments and decisions. In other words, the market is not a weighing machine, on which the value of each issue is recorded by an exact and impersonal mechanism, in accordance with its specific qualities. Rather should we say that the market is a voting machine, whereon countless individuals register choices which are the product partly of reason and partly of emotion.”
Found via Value Investing World.