Sell Half? from Ralph Vince

August 23, 2011 |

It's my experience that if you need to sell a portion, even if that portion is 100%, via a stop order, you're in too heavy to begin with. Being in too heavy is to be too dependent on luck.

Dylan Distasio writes:

Ralph,

Can you expand on your definition of "need"? Let's use the case of HPQ as an example. x had an investment hypothesis that no longer necessarily holds true after the potential value destruction of recent company decisions. As a result, he decides to liquidate half. Maybe someone else gets in a few weeks ago after the discussion on HP here, as they agree it looks like a value play, but they have a rule to always attempt to minimize losses on new positions to a flat 10% to protect capital and to always use stops because they need them for discipline. So they get a ~20% haircut after getting stopped out on the gap down.

I'm not sure either situation of a 50 or 100% liquidation was based on what I would call need, but rather some kind of capital preservation or very basic risk management rules.

In all serious, how would you define need as I think it is worth looking into this further? Potential loss of all capital? Forced margin liquidation? I agree that being in with too much leverage or too large a position opens you up to getting taken out by noise, but what is need versus risk management?

Chris Cooper writes:

I took a big loss on Monday of the week before last. I then cut my trade size in half, and manage to end up flat at the end of the week. The week actually would have been very profitable had I been willing to stay with my original sizing. But Ralph is correct, and I decided that if I am getting scared by a big daily loss, I'm trading too heavy, so I have left the trade size at that halfway point.

On the other hand, one might choose a rule that pares back the trade size when volatility increases. These were intraday forex trades, and clearly that week was exceptional in terms of volatility. The problem is that the volatility spikes that kill me do not appear to be predictable. Therefore I have to trade most of the time at a level that seems relatively placid in order to avoid being frightened into damaging behavior occasionally.

Gary Rogan writes:

I think this illustrates the point I was trying to make originally about the lack of logical underpinnings in the "sell half" decision: it's an emotional decision because you (a) get scared by the suddenness and violence of the move an its effect on your net worth (b) belatedly realized that you were in too much. Now the second part is sort-of logical, but it really points to the lack of imagination about what a position can do when you get into it: you imagine a slow gradual move and the thing suddenly loses a big chunk of its value without much warning. This is not theoretical for me, because for the first time ever I have faced the following: two days after buying a stock it suddenly loses 25% of it's value in a day. This happened TWICE in a row on top of that, and only underscored to me that you never know enough to say with confidence that you will not lose all, and quickly. Therefore you should assume that that's the case from the very beginning.

Ralph Vince replies:

Dylan,

I'm really referring to liquidity concerns; Rocky's decision to liquidate half, I assume, is a risk-management procedure here, as opposed to a strategic one based on changed fundamentals (I may be, and, in retrospect, likely am wrong about this!).

Any risk-management concern where someone "needs" to get out, shy of that investment being entirely wiped out, will, in time, be entirely wiped out, or damn near whether by an Enron, or those gilt-edged AAA GM bonds at one time.

Dylan Distasio responds:

Gary,

Although I don't typically trade that way, I don't think the sell half is necessarily an illogical or emotional decision depending on the scenario. We have no way of knowing what the reason behind selling half is for a given individual. Reducing a losing position size is, in my mind, a way to mitigate risk of additional loss while still having some skin in the game. Keeping some powder dry is (I would imagine as an amateur) one of the more important survival skills in this game. The person selling half doesn't have to be in too deep to their overall capital pool to want to protect half of what remains of that position based on changing circumstances. Losses do add up over time.

Alston Mabry writes:

I have found that trading breaks down into (1) analysis, and (2) execution. With "analysis" being a period of calm, quiet reflection (maybe with a cold beer) over a crowded spreadsheet; and "execution" being whatever I have to do to manage my lizard brain once there is real money at stake. They can be such radically different modes of being that sometimes it's very difficult to establish a link.

If I make "analysis" and "execution" the axes of a graph, I can place each of my trades on the graph in the appropriate quadrant: {analysis(good), execution(good)} = exhilaration, {analysis(good), execution(bad)} = regret, {analysis(bad), execution(good)} = relief, {analysis(bad), execution(bad)} = self-loathing.

The challenge of trading is that there is only one quadrant you *want* to be in.

Chris Cooper adds:

Rocky wrote:

"I challenge anyone to demonstrate a single person who blew up while sticking to the rule: "Only add to a winning position.""

I can't meet your challenge, but I did have a week where I lost 50% of my equity. Your observation does not apply to those trading with leverage. I am now learning to scale back the leverage, make adjustments in trade size more frequently than weekly (should be real-time), and to write models which account for higher correlations during times of stress.

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