The problem with short gamma

Discussion in 'Options' started by nitro, Mar 20, 2010.

  1. nitro

    nitro

    Right, that is why you want something like a VS. The whole is almost equal to the sum of the parts in VSs, so aggregrating accurate book risk is possible. This is attained by the inverse of strikes-squared weighting scheme. If strikes were continuous instead of discreet and you could put on an infinity of option positions on at these strikes, you would never need to hedge the underlying at all. Alas, that is one of the big problems with BS as it assumes that you can continually hedge, at zero cost.

    This does not go far enough. You also need to understand the options own sensitivity to the skew, which is also non-linear but can be approximated roughly so for small underlying moves and time. In the presence of jumps, the whole thing becomes incredibly complex.
     
    #81     Mar 29, 2010
  2. If there were continuos strikes and perfect dynamic hedging, we would either all be out of business, or trading long gamma.
     
    #82     Mar 29, 2010
  3. +1, there would be no need of options :p .
     
    #83     Mar 29, 2010
  4. nitro

    nitro

    Well, that is what a Variance Swap gives you, with the "dynamic heding" priced in. With a VS, you are no longer trading the underlying (mean), but something far closer to pure vola.

    There are still risks, but the mean is almost completely removed from PnL for a long stretch of strikes, as seen by the almost flat gamma profile.
     
    #84     Mar 29, 2010
  5. When you cut through all the posturing and buzzwords, OP's real issue is: he wants to sell premium but is annoyed the markets have sustained directional moves, thus he gets hurt more than he "should" based on stdev or some other simple measure of vola. But.. the market's <i>job</i> is to inflict pain on whatever strategies are popular. The fact that iv has drifted down for the past year means there are more premium sellers than buyers. All those sellers are at risk from sustained directional moves. So what's the market going to tend to do? An exercise for the reader.
     
    #85     Mar 29, 2010
  6. nitro

    nitro

    That is false.

    That is true.

    That is false

    Irrelevant in my case.

    In fact, the popular strategy has done extremely well. Buy stocks, sell calls against it. Not as well as, throw a dart a the WSJ stock lists page and just buy stocks, but then, that is only in retrospect.

    http://finance.yahoo.com/q/ta?s=^BXM&t=1y

    If you don't want to deceive yourself, your true measure of continued success is to compare your gains against some index that mirrors the way you trade, and then see if you have alpha above and beyond that index. If someone says to me, I am up 70% from last march, I would say, oh, you bought the SPY last march and shut down your computer, aye?
     
    #86     Mar 29, 2010
  7. Re buywriting, it's ~putselling (yes, there are second-order differences, don't bother) so of course it does well when the market drifts upward. Buywriters are hurt by market crashes.

    As to "up 70%" & etc., I agree with OP that performance against a benchmark is the correct measure -- for a mandate-constrained trader. It's less clear for someone trading his own account.
     
    #87     Mar 29, 2010
  8. nitro

    nitro

    #88     Oct 19, 2011
  9. Nitro,

    Have you ever done any cointegration or RV testing for VS trades?
     
    #89     Oct 19, 2011
  10. nitro

    nitro

    No. The reason is that I am data starved. But I think the new systems are looking at porfolio level and book level PCA and Cointegration/RV analysis.
     
    #90     Oct 19, 2011