But why does the amount of premium you pay for the futures always vary? right now you are paying 15 points for the front month, i seem to recall it being as low as 6, this is probably a dumb question but what causes the variance? I realize the S&P is an index based on the stocks cash price but shouldnt there always be some kind of arb price between cash and futures? Is it just because people are jacking the futures to try to make stocks go up and people dont believe it? Is there any set variable that will determine the difference between what the S&P cash and futures should be trading at?