Bum--
You wrote, "Credit spreads are much less risky & have lower margin requirements."
Consider the following modifications to the example you gave:
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Here's an example:
XYZ trading @100
Sell ten 90/80 put spreads for $2 each.
XYZ goes to 80.
Trade result: I lose 8 * 10 = $80.
Same stock example except I sell 90 naked put for $4.
Trade result: I lose $6.
Compare:
Put spreads lost $80, which is 100% of $80 net margin.
Naked put lost $6, which is 7% of $86 net margin.
So would you rather lose $80 (100% of trade margin) or $6 (smaller % of margin)???
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The credit spreads had a lower margin requirement while using less leverage [where leverage = total assets / total equity (and assets = notional value)].
Would you still say the credit spread position is much less risky?