Quote from Maverick74:
Haircut on the SP is 6% to the upside and 8% to the downside. Yes, it is fixed. The problem with span is it's variable margin. Meaning it can go up on you without notice and force a liquidation. And it usually happens at the worst possible time during a big selloff. I've seen span margin double overnight. And if you can't meet it, they liquidate. Span also does nothing for the long gamma trader. In other words, when you buy options, you have to pay 100% of the premium. Span is only useful if you sell naked options.
Also with span, you can't mix and match products. If you trade ES options, you will get relief on your margin if you trade ES futures against it, but nothing else. With a haircut, you can trade, spy options, es options, spx options, oex options, spyders, even dow, nasdaq, russell options and futures and ETF's and get haircut relief on all those products as one big position.
There really is no comparison between the two. Span is very limiting. Haircut and cross margin is much more flexible and all encompassing.
For haircut margin, the maintenance margin will change with the index level. Is it MTM? So we still need to have a cushion for the margin change.
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