Kelly Criterion & Risk Of Ruin As Risk Management Tool

Discussion in 'Risk Management' started by ironchef, Jul 4, 2017.

  1. rvince99

    rvince99

    No, I don't. Sorry. It would be a great idea though for some sort of intern, I'll look into it. It an also get pretty computationally intense & lengthy (its a genuine distributed processing problem as the number of components starts to increase).

    It gets even more intense when we look to solve for criteria other than just being "expected growth-optimal (all else be damned)." For example, most of us want growth withing some sort of constraint. One common measure might be, say, expected growth with respect to amount risked as far better criterion than just what many colloquially refer to as "Kelly," but I refer to (for the sake of accuracy) "Expected growth-optimal."

    Such a thing is solvable by the same equation, optimized for a different target, but it gets a little mind-bending for most: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=2364092
    and the slides to a talk one of my coauthors did on it (perhaps a little simpler):
    https://papers.ssrn.com/sol3/papers.cfm?abstract_id=2624329
    That's all theoretical though, and since I manage two hedge funds, like most traders, I have the day-to-day real world slog of bridging the theoretical with the real world. So much of my time in recent years has been spent on robust approximations which can be implemented i the markets themselves, realizing there is a big difference between the academic world and the trading world (and I come from the latter). So my efforts have been along the lines of:
    -How can you define the shape of this "manifold" without going into heavy math, doing it simply, with fair approximations?
    -How do you travel through this manifold, i.e. what quantity should i have on at present to satisfy my criteria in the markets with respect to current risks, capital available, etc. and do so in a manner tht doesn't require supercomputers solving very complex equations running parallel! I am i the day-to-day foxhole of the markets and I need robust tools that will work for me there.
     
    #171     Jan 7, 2018
    Xela likes this.
  2. MrScalper

    MrScalper

    i often wonder what emphasis those in charge of large hedge funds place on identifying the best people to trade relevant markets..one is led to believe that those with high IQ and best head for maths land the best paying jobs..but..if these people were to trade their own money..would they take the same risks..just wondering!!

    one chap that can teach anyone an awaful lot about trading or investing is Harry Markopolos!!
     
    #172     Jan 7, 2018
  3. ironchef

    ironchef

    Thank you Mr. Vince for your thoughtful post. It will take me a while to digest your post and especially your paper on Growth Optimal Fraction. My layperson's understand of what you meant by growth optimal fraction is what we call the Kelly?

    I am math challenged and will never be able to understand let alone derive the optimal fraction. However, most of us traders instinctively determined that it is much "safer" for us to trade with a fraction much less than Kelly (e.g., 1/4 Kelly) in order to avoid the risk of ruin.

    The most provocative thought for me is this:

    As a purchaser and writer of options this is actually very helpful. Thank you.

    PS: I hope you can provide me with answers if I have questions after digesting your paper.

    Regards,
     
    #173     Jan 8, 2018
  4. rvince99

    rvince99

    I'll do what I can to answer things (I'm just learning myself, though that's been going on for decades on this obsession of mine).

    Yes.

    (And FWIW I am "Math challenged" too).

    Yes, very true -- most people's criteria in trading does not encompass seeking "expected growth-optimality, all else be damned." Most people have a risk concern/constraint, and this therefore implies trading some sort of quantity calculation more towards zero and away from the peak (what people refer to as "Kelly"). And every discussion about these diluted allocations are ad-hoc, capricious and absent any rigor because the dynamics of that region haven;t been examined, and I've tried to do that and my point is there are values in that diluted region that are more "optimal" to us, as traders, with our risk considerations, than just mere growth-optimality.
    .
    Interestingly, to the "right" of the peak, that is, the insane region between the peak and 1.0, is an area with significant geometric consequences to situations where one would seek growth diminishment. We don't often consider that since, as traders, we are concerned with growth. Yet there are many functions in human experience where the curtailment of growth is desirable (e.g. federal debt, pathology, etc.) which the material is germane to.
     
    #174     Jan 8, 2018
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  5. ironchef

    ironchef

    You may find this interesting:

    https://papers.ssrn.com/sol3/papers.cfm?abstract_id=2259133

    Regards,
     
    #175     Jan 8, 2018
  6. rvince99

    rvince99

    I'm familiar with it. Interestingly, the academic community is painfully behind what the gambling and trading community has been doing in this arena (and in large part, because we have not played by their rules, and they have made little attempt to do anything but build on past endeavors in academia, to their detriment).

    This work was first performed (to the best of my knowledge) by a guy named Mike Pascual, in Vegas, who introduced it for multiple, simultaneous sports book gambling with an edge. It was circulated but unpublished. I have an original mimeograph of his hand-written book (and code) at a home I have in another state. I don;t know if Mike is still with us.
     
    #176     Jan 8, 2018
  7. %%
    Good point Mr Scalper; overtrading for me, also includes.......NOT have too big of a comission to profit ratio.
    Never bought in to strange idea trading/investing had to be boring; but that could mean the same as panic sellers/buyers never win.Planned sellers/buyers can win. Agree always be kind to animals, but i seldom put up with a biting or clawing animal:D:caution:
     
    #177     Jan 8, 2018
  8. MrScalper

    MrScalper

    sometimes i wonder how i was so silly in the past..i remember coming back from an occasion..we all headed to the local pub after for some drinks..after about 1 hour i left and went home..turned on my pc..and logged into woodie giving a chat about his magical method for short term trading the ES..the famous woodie's cci..all i will say is that i now laugh at how silly it all was..i wasted about an hour and went back to the pub :)
     
    #178     Jan 9, 2018
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  9. ironchef

    ironchef

    It is time for me to summarize what I get out of this thread. Anyone disagree or have other ideas are welcome to comment:

    1. It is beyond my ability to derive the equations of or comprehend Kelly or Growth Optimal Fraction but intuitively, I came to the realization that trading at fraction Kelly will lower my risk of ruin.

    2. If there is no positive expectancy, risk of ruin is a certainty, Kelly or Growth Optimal Fraction be damned. So, I should definitely determine if my method has any positive expectancy before even trying to determine Kelly or Growth Optimal Fraction.

    3. Kelly, or Growth Optimal Fraction do not deal with risk of ruin, only optimal growth? For one without infinite funds, and non asymptotic trades, one better trades with a fraction of Kelly or Optimal Fraction or else risk of ruin can easily wipe out one's account.

    4. For low win rate methods, like long DOTM options, assuming positive expectancy, to get positive returns, one should execute a large number of trades to capture the occasional "lottery type" winning potentials. So, trade often and trade small.

    5. For high win rate methods, like shorting DOTM options, again assuming positive expectancy, perhaps one should limit the number of trades and try to avoid the occasional "black swans". So, trade a few times with huge leverage then retires, riding into the sunset! :cool: Trade often and trade small is the wrong way to go, counter the coaching of websites like tastytrade?
     
    #179     Jan 9, 2018
  10. It's not that complicated, really. It comes down to this: to figure out your optimal position size, find the leverage that maximizes the sum of log-returns of your past trades. Then trade with a fraction (such as 0.25) of that leverage.

    Yes, it gets more involved when you have to deal with portfolio allocation where you may need to trade (and hold positions in) multiple instruments at the same time, and to allocate for the specific time horizons. This is where it gets computationally intense.
     
    #180     Jan 10, 2018