You'd have better luck predicting a coin toss based on starting velocity, wind speed, ambient humidity, etc., than you would predicting a stock's day-to-day movement based on all available data.
How does efficient market theory explain all the millionaire and billionaire stock traders Manhattan and London? People who claim it's impossible to make money trading simply don't know how to trade. With the exception of Communism, Milton Friedman's BS theories on efficient unrestrained capitalism have done more to destroy the world economy than any other intellectual movement in modern history.
Those who can, do; those who can't, simulate.