First you must remember that the markets are the people, the number represents EVERYTHING put together.
That being said, trying to include ALL the inputs of some stock is IMPOSSIBLE and VERY INEFFICIENT.
One of my professors once told me a story that NASA had some new program that had thousands of input variables and was supposed to be the best thing since silicon implants :P Well, it was so complicated that they never managed to get it to work and get results as good as much simpler models.
They brought in an expert that reduced the complexity ten folds and by approximations simplified the model and it only needed a couple of dozens of variables, only then the program worked properly and showed what it's worth.
Getting back to finance, I don't know if you're familiar with communications theory but many times even though you have and can use more empirical data it is simpler and on average gives a better return to just model the noise as a random variable.
Same thing in finance, I guess that many models have some slowly moving baseline and on it they insert the faster "noise", trying to model it too detailed will only backfire in terms of computational effort and time of response.
It's better to have 60% success with a HUGE volume than having 80% on a much SMALLER one.
