A strategy can look remarkably safe for years and still carry enormous risk. When it finally breaks, the cause is usually not a bad forecast. It’s the shape of the exposure.
The profile is familiar once you know to look for it. Small gains arrive month after month, volatility looks low, and the track record looks reliable. Then one event gives back years of gains, sometimes more than that. Selling insurance against unlikely events works this way, and so does any strategy that collects a little when nothing happens and pays a lot when something does. That shape is concave: capped, frequent upside and an open, infrequent downside. The danger is that it looks like skill right up until it doesn’t, because the risk never shows up in the volatility statistics until the event arrives.
Convexity Reverses the Structure
A convex exposure constrains losses deliberately and lets the upside become disproportionately larger. It can be wrong repeatedly and survive, because each wrong is small. A sufficiently concave exposure can be right repeatedly and still eventually fail, because the one wrong is large enough to erase all the rights.
That doesn’t make every convex position attractive. Convexity has a price. Options decay, insurance carries a premium, and a large theoretical payoff doesn’t by itself create a favorable expected payoff; it can be a slow bleed dressed up as protection. The point isn’t that convex is good and concave is bad. The point is that payoff shape changes the consequences of being wrong, and being wrong is the one thing we can count on happening.
The First Question
That’s why we don’t begin portfolio management by asking what we think the market will do. We begin with a different question: what happens if we’re wrong?
From the answer, we define the exit, the point where the position has told us the thesis isn’t working. From the exit, we size the position, so the planned risk fits the portfolio’s risk budget. Only then do we consider the upside, and we consider it as a shape rather than a point estimate: what does the exposure do if we’re right, and how much of it do we get to keep?
A forecast describes what we expect. The payoff structure determines what happens when reality is different, and reality is different often enough that we build for it first.
That’s ASYMMETRY®.
Mike Shell is the founder and chief investment officer of Shell Capital Management, LLC, a registered investment adviser. He serves as portfolio manager of ASYMMETRY® Managed Portfolios, a separately managed account program with trade execution and custody provided by Goldman Sachs Custody Solutions.
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