I was wondering if anyone has experience trading SDS. It is supposed to be 200% the inverse movement of the S&P 500. But when i was looking at it today and it seemed to only be around 80% of it or so? anybody know why? is it 200% movement per notional dollar? i notice the price of SDS seems to be 1/3 the price of SPY. so if i have 30k$ spy does that mean i should have 15k$ of SDS to be hedged? or 50% of the # of SPY lots?