Subsets and Sensibility

One of most dangerous habits of a speculative crowd is the tendency to use unconditional averages and unconditional probabilities regardless of how extreme market conditions have become. This is like stepping into a house with two rooms, one with the temperature at 0 degrees and one at 140 degrees, and expecting a temperature of 70 either way.

The fact is that market outcomes differ based on varying market conditions. If one thinks of positive and negative market outcomes as being distributed across a “bell curve,” the position and shape of that bell can differ substantially depending on a wide range of factors, including the level of market valuations, the stance of monetary policy, the psychology of investors toward speculation or risk-aversion (which we infer based on the uniformity and divergence of thousands of individual stocks, sectors, industries and security-types), and shorter-term overextension and compression of market action.

It’s difficult to find subsets of market conditions that are historically associated only with market advances or only market declines, and it’s impossible, I think, to identify conditions of this sort that apply to any significant portion of market history. Rather, nearly all of the market conditions we identify are associated with a distribution of both positive and negative outcomes. It’s just that the features of the distribution – its average returns, the frequency of extreme gains or losses, and the time-horizon of the most reliable outcomes, can vary enormously across various conditions.

Graham and Dodd emphasized the danger of “unconditional” investment behavior in their 1934 discussion of the market collapse of the Great Depression – which I could still reprint in every market comment here, and be satisfied that my readers had been served well.

benjamin