Information characterizing a company’s value isn’t the same thing as information indicating a company’s value. There can be a lot of analysis and model building in between. And different models can behave very differently, even if their prediction strength is similar.

Information publicly available doesn’t mean anyone can process it all. Every actor is operating off a different subset of information.

Lots of intentionally low information investors (inhabitants of indexed funds) demand stock or supply stock, pushing prices in directions unrelated to value changes, due to index list changes and rebalancing events.

Investors, of all magnitudes of wealth, have unending personal or private idiosyncratic reasons for the timing of many investments or sales, besides individual asset return optimization.

The value of a stock rises and falls as its absolute expected return rises and falls relative to the changing returns of the rest of the entire market of investment vehicles. Everything impacts everything.

All these shifts happen over varying time frames.

Almost all relevant market facts are time varying, often with turbulence and ambiguity.

The fast moving investors most influential in setting prices, must model the whole market’s 2nd order and even 3rd order reactions (by similar actors) due to feedback effects and dynamics.

Sudden market wide changes trigger waves of low analysis buying and selling. Compounded by the higher order risk this creates to leverage, annuity responsibikities, hedging, and many other amplifiers of behavior.

The efficient market hypothesis is an interesting and enlightening thought experiment. A reduced dimension toy/sim market.

Not a credible model.

Not even if every single participant was frantically and relentlessly re-valuing and re-balancing at the margins to a firehose of comprehensive market information.