Back in my portfolio manager days, I was a really good short seller. I say that as a factual observation, not a brag, as it’s not a skill set that’s driven by some great intellectual or character virtue. On the contrary, most short sellers are, like me, highly suspicious of all received wisdom (even when it is, in fact, wise) and have weirdly over-developed egos that feed on the notion of “I’m right even though the world says I’m wrong”. But what set me apart as a short seller were two accidents of experience. First, I didn’t come out of Wall Street, so I wasn’t infected with the long-bias required of those business models. Second, my professional career prior to investing was all about studying mass behaviors and the informational flows that drive those behaviors.
Here’s why that’s important. The biggest difference between shorting and going long is that shorts tend to work in a punctuated fashion. One day I’ll write a full note on the Information Theory basis for this market fact, but the intuition is pretty simple. There’s a constant flow of positive information around both individual stocks (driven by corporate management) and the market as a whole (driven by the sell-side), and as a result the natural tendency of prices is a slow grind up. But occasionally you’ll receive an informational shock, which is almost always a negative, and the price of a stock or the overall market will take a sharp, punctuated decline. The hardest decision for a short seller is what to do when you get this punctuated decline. Do you cover the short, pocket a modest gain, and look to re-establish the position once it grinds higher, as it typically does? Or do you press the short on this informational validation for your original negative thesis? It’s an entirely different mindset than that of most long-only investors, who – because they have the luxury of both time and informational flow on their side – not only tend to add to their positions when the stock is working (my thesis is right, and I’m raising my target price!) but also tend to add when it’s not working (my thesis is right, and this stock is on sale!).