Relative strength calculations rely on a single input: price. We like price because it is a known quantity, not an assumption. In this deconstruction of the Price-to-Earnings Growth (PEG) ratio, the author, Tom Brakke, discusses all of the uncertainties when calculating even a simple ratio like PEG. And amidst all of the uncertainties he mentions is this:
In looking at that calculation, only one of the three variables has any precision: We can observe the market price (P) at virtually any time and be assured that we have an accurate number. The E is a different matter entirely. Which earnings? Forward, trailing, smoothed, operating, adjusted, owner? Why? How deep into accounting and the theory of finance do you want to go?
For most investors, not very far. We like our heuristics clean and easy, not hairy. So, in combining the first two variables we get the P/E ratio, the “multiple” upon which most valuation work rests, despite the questionable assumptions that may be baked in at any time. The addition of the third element, growth (G), gives us not the epiphany we seek, but even more confusion.
The emphasis is mine. This isn’t a knock on fundamental analysis. It can be valuable, but there is an inherent squishiness to it. The only precision is found in price. And price is dynamic: it adapts in real time as expectations of the asset change. (Fundamental data is often available only on a quarterly schedule.) As a result, systematic models built using relative strength adapt quite nicely as conditions change.
—-this article originally appeared 2/10/2010. We still like using prices as an input, especially now that there are so many cross-currents. Every pundit has a different take on what will happen down the road, but prices in a free market will eventually sort it all out.