Posted margin as the scarce input of an option-income write

What the snapshot held fixed

The 2003 snapshot compared two option-income procedures at the same December expiration and the same percentage distance from the money: a naked out-of-the-money call and a call credit spread. Inputs were settlement prices from 25 September 2003 with 84 days remaining. Volatility was not treated as a separate adjustment because the two equity-index underlyings were taken to share similar volatility patterns.

The option-income strategy is the testable short-premium procedure that specifies strike distance, expiration, entry, exit, and stand-aside conditions for collecting a credit over one holding period. Margin management is the pre-trade and in-trade filter that bounds exposure from account equity, volatility, remaining life, and stop or strike-width distance before a write is sized.

Naked out-of-the-money calls

Margin per dollar of premium is initial posted margin divided by cash credit received. Premium as a share of margin is the inverse score: collected credit divided by initial margin. Those two ratios are how this snapshot compares how much capital a write ties up per unit of income.

For a 10% out-of-the-money cash-index short December 550 call, exchange-minimum cash-index margin after the out-of-the-money offset was $2,500 against $420 of premium, or $5.95 of posted margin per dollar of credit (16.8% premium as a share of margin). Exchange-minimum cash-index margin is a percentage-of-underlying formula reduced by the out-of-the-money amount.

Futures-option premium was restated to a fair-value futures level so a matching 10% out-of-the-money December 1100 short call could be compared. SPAN initial cash requirement was $7,425 against $1,600 of adjusted premium, or $4.64 of posted margin per dollar of credit (21.5% premium as a share of margin).

Scaling those uncovered-call premium-to-margin ratios to $100,000 of notional margin produced $16,800 of credit in the cash-index case and $21,500 in the futures-option case.

Margin engines, not exercise style

Both listings were American-style, so early-exercise rights were not the stated cause of the margin gap. The futures-option requirement used a SPAN margin engine that takes volatility, remaining life, and moneyness as inputs rather than a single percentage of notional. The cash-index uncovered write used the exchange-minimum cash-index formula.

The same distance as a call credit spread

A call credit spread is a net-short call that buys a farther out-of-the-money call so maximum loss equals strike width minus net credit. The cash-index December 550/560 call credit spread collected $200 net against $1,000 of strike-width margin, or $5.00 of margin per dollar of credit (20.0%). That is only a small change from the $5.95 uncovered-call figure, while collecting 52% less premium.

A matching-distance futures-option credit spread collected $600 net against $1,491 of SPAN initial margin, or $2.48 of margin per dollar of credit (40.2%). Scaling those credit-spread premium-to-margin ratios to $100,000 of notional margin produced $20,000 of credit in the cash-index case and $40,240 in the futures-option case.

How the filter reads the two overlays

Editorial: the cash-index overlay left margin per dollar of premium almost unchanged and collected much less credit, so it does not, on this snapshot, change how many bounded writes fit once capital is the scarce input. The futures-option listing already posted less margin per dollar of credit on the naked write, and the matching credit spread moved that ratio again.

Editorial: the short-call rule stays the object under test. A change of listing venue or a defined-risk overlay is accepted only when that venue's margin engine changes credit collected per unit of capital enough to alter how many bounded trades the account can hold. The snapshot ranks those capital-use differences. It does not rank later profitability.