It takes more than a little math. I hang out in stock market chats that have a lot of programmer trying to do just this, and this comic is completely accurate: http://xkcd.com/1570
I often wonder where Randall Munroe gets all his wisdom.
edit: I didn't mean for this to be disparaging remark: I am genuinely impressed by how wise he is about so many topics, given that he is only 30 years old.