All the existing system you use, just look at the latest price, and compare it to the past. It can be as simple as moving average technical analysis, or some very convoluted algorithm.
Imagine that for some peculiar reason, there is a correlation between the stock market and something else, that is totally unexplainable.
What will you do?
Will you ignore it?
No. You will cynically keep an eye on it, to hope that it will fail.
Next you will fight your cynicism.
Next you will really believe it.
Next you will be totally confused.
Welcome to the world of stock market astrology.