> If you know how the stock market will perform in detail far in advance, though, rather than sit on a single tip about some deal, you can do amazingly well by moving sufficiently small amounts into each of a bunch of shares sufficiently long in advance that it'd be just noise.
If, however, you consider the stock market to be a chaotic system, your small trades will change the market's performance.
We should assume that, but that affects your ability to make predictions to some extent past the moment you arrive, and so you may find your knowledge quickly becomes out of date, but you don't need to be 100% right - your knowledge needs to remain "close enough" for you to beat the odds with some reasonable margin.
If, however, you consider the stock market to be a chaotic system, your small trades will change the market's performance.