Originally posted on 08/28/2013:

Guy loaded with machine guns comes to a broad side of the barn and randomly sprays it with a thousands of bullets.
Then he watches his results for a long time and very thoughtfully picks the largest clusters of the bullet wholes produced by his random shooting.
Then he takes a paint and draws bulls-eyes centered around the largest clusters.
Then he proudly declares himself the best sharpshooter in his country.
Is he?

I doubt it!
It seems to me, that his specific hypothesis ( "I am the best sharpshooter in a country and will hit the center of bulls-eye more often then anyone in the country")
should be confirmed by data (results of the firing over existing bulls-eye).
Collecting data first and then trying to invent specific hypothesis (in your case it would be "predictive formula") based on already collected data is not exactly
the smartest approach. In fact, it seems to me like an excellent way to get in a poor house.

Bottom line.
You can watch your past data all you want trying to discover hidden jams of undiscovered predictive patterns.
This is, by far, one of the favorite pass times of the human brain. Science even has a term for this - apophenia.
But once you done having this fun and think you got your golden nugget, this gut feeling of yours must be independently confirmed to the point of statistical significance by NEW, CLEAN set of data WITH NO TWEAKING ALLOWED. NEVER. EVER.