intraday time decay?

Discussion in 'Options' started by leorc, Sep 9, 2009.

  1. spindr0


    Good explanation. I think that now, I understand what I was saying :)

    OK, I've had a nap and it all makes sense... I should probably stop here :)

    Given that:

    Stock + put - carry cost = call (assume no dividend)

    If we're looking the 180 options with IBM at 100, would it be fair to say that if the call is worth zero since it's so far of the money, the discounting of the put comes from the carry cost?

    Stock + (put - carry cost) = 0

    IOW, the put goes for less than intrinsic and that's essentially what you said about the pricing model having a heart?

    Or IOW2, if the forward price of IBM is being used and if the call premium is higher than the put premium then if the call premium is zero then the put premium must be less than zero (sort of a negative extrinsic) which means that the put might be 79.19 (as per your 81 cent carry cost example) despite being 80 pts ITM?
    #21     Sep 13, 2009
  2. dmo


    With American-style options, the option can't be worth less than intrinsic value. That's because if the cost of carry of the option becomes too great you can always just exercise the option and realize its intrinsic value. But with European-style options yes, the cost-of-carry discount can bring the option's fair value under its intrinsic value.
    #22     Sep 13, 2009
  3. I am not sure I am correct, as I forgot what theta etc. means, but I guess your question about intraday time decay comes down to:
    1) is interest calculated overnight or real time? > overnight as far as i know, therefore there shouldn´t be intraday time decay.
    2) time decay as in volatility risk until time of expiration: I suppose for every second the option loses time and therefore risk, theoretically there should be intraday decay, albeit inmeasurably small probably in most practical cases.
    #23     Sep 13, 2009
  4. spindr0



    Occasionally I gamma scalp a straddle. Given the discussion of carry cost and theta of puts versus calls, I wondered if it made any difference whether one just used calls or just puts?

    For example, I took a straddle position late last month. For each straddle bot, I also bot 18 shares to start off delta neutral.

    At that time, I could have bot 2 calls and shorted -118 shares or I could have bot 2 puts and bot 82 shares. These two positions would also have been delta neutral (not sure if it's relevant but adding these 2 would be the same as doing 2 straddles and 36 shares).

    Given that carry costs make calls pricier than puts, is there an advantage to doing this with stock and puts versus those the other combinations that involve calls? And given that my broker pays bupkus on cash balances, wouldn't that tilt things further in the direction of lower cost puts?

    #24     Sep 20, 2009
  5. For gamma scalping, is it better to enter a long straddle or a synthetic straddle?

    Although the synthetic saves on the theta decay, as well as an adverse impact to implied volatility, it does give up the positive effect of delta & gamma because as the strike moves farther OTM, the delta & gamma reduction softens the adverse impact of the loosing leg. Also, if IV is increasing, that also helps the loosing leg.

    One more thing... more leverage with a long straddle than a synthetic long straddle...

    Any thoughts on which is better...


    #25     Sep 20, 2009
  6. dmo


    Spin, you seem stuck with this idea that carry cost makes calls more expensive than puts. It doesn't. It just changes the underlying price from the current price to the forward price.

    In any case, it's a moot point. With T-bills currently yielding about zero, you can reasonably use a cost of carry of zero, which eliminates the whole problem entirely.

    As for your other question - if we're talking about options on futures, then I can say absolutely, positively, in both a theoretical sense and a real, street-level, practical sense, no, it doesn't matter whether you're long straddles, puts, or calls. If we're talking about, say, the 1000 strike, you can be long 50 calls and no puts, 50 puts and no calls, 25 calls and 25 puts, or 5 calls and 45 puts. As long as your delta is the same there is really, truly, honest-to-god no difference.

    Theoretically there is no difference with stock options either, but practically there may be additional considerations. You could run into a hard-to-short situation so if you buy calls you may find it difficult or expensive to sell stock against it. It's possible the short stock could be called away, leaving you with no hedge. There may be different margin implications.

    So for gamma scalping with stock options, you're probably better off buying puts and buying stock against it. That way you can scalp gammas to your heart's content and never have to sell stock short.
    #26     Sep 20, 2009
  7. dmo


    Where on earth do people come up with such misconceptions?

    There is a reason that a position consisting of a long put and a long underlying is called a "synthetic call." It is because a synthetic call has the same gamma, same delta, same vega and same theta as a natural call.

    The same is true for synthetic puts, synthetic underlyings, and synthetic straddles.
    #27     Sep 20, 2009
  8. spindr0


    OK, I'm stuck on that idea and I have no clue how the forward price factors into what I think I'm seeing.

    Let's try a hypothetical. Priced today (theoretical), a $50 stock has the following:

    $4.16 = Nov 50c (delta = .545)
    $4.04 = Nov 50p (delta = .455)

    other than the natural straddle +/- stk, delta neutral could be:

    buy 2 Nov 50c and short 109 shares
    buy 2 Nov 50p and buy 91 shares

    With the call position, the option component cost me 12 cts more per synthetic staddle. Now it may be obvious to you but I have no clue where I make that extra 12 cts per syn straddle so that the result is the same as the person who does the put side.
    #28     Sep 20, 2009
  9. donnap


    Hi Spin,

    Of course, your example assumes much higher interest rates than today's rates.

    The extra .12 comes from interest paid on short sale proceeds.

    We both know that the ave. retail doesn't earn i on short proceeds and for now we pay - but the option pricing assumes that we are all MMs - lol.
    #29     Sep 20, 2009
  10. My aim was Not to compare a synthethic call with a natural call, as I recognize the greeks are the same.

    What I was trying to do was compare an option leg with a stock position(obviously my attempt was poor). For example, is it better to have a long put & a long call or a long stock and a long put? Although having the long stock position instead of the long call would reduce the impact of theta & a drop in IV, on the flip side it looses the benefit of delta & gamma...

    Am I wrong here??? Nonetheless, which is better, especially considering the leverage factor...

    #30     Sep 20, 2009