The best mathematical model we currently have for stock markets is as follows.
You wake up and walk to your desk.
On your desk are your wads of cash.
You grab all your wads of cash and leave the house.
If you see another investor you throw random amounts of cash at them.
They do the same to you and you pick up that cash.
After a day of walking around town you go home.
You put your wads of cash on the desk and go to sleep.