The intent of this series of posts is to put my later posts about specific investment ideas in context, by describing the evolution of my thinking on investing over the last year and a half, as I've made mistakes and tried to learn from them. I'm going to break this up into a few posts, just to keep each post from being too long.
The Magic Formula
For those unfamiliar with the Magic Formula, it's Joel Greenblatt's Buffett- and Graham-inspired mechanical system of buying a basket of "good" and "cheap" stocks. From Graham, Greenblatt got the emphasis on buying a basket of cheap stocks. In the Magic Formula, Greenblatt uses earnings yield, defined as EBIT/Enterprise Value, to measure "cheapness". Greenblatt uses EBIT instead of earnings to account for differences in interest payments and taxes among different companies, and he uses enterprise value instead of price to account for different levels of net cash or net debt. From Buffett, Greenblatt got the emphasis on finding "good" companies, defined as companies with high returns on tangible capital. Greenblatt calls this return on invested capital (ROIC) and defines it as [EBIT/(Net working capital + Net fixed assets)]. Greenblatt set up a website, Magic Formula Investing.com, to make it easy for individual investors to follow this system. The site ranks its universe of thousands of (mostlyAmerican) stocks by earnings yield and by return on invested capital, and lists those stocks that have the best combined scores (i.e., not necessarily the "cheapest" or the "best", but the stocks that represent the best combination of "cheap" and "good" according to the system).
After reading Joel Greenblatt's The Little Book that Beats the Market in late 2006, I began investing the better part of my money according to the methodology in the book in early 2007. During this time, I read a number of books on value investing (e.g., The Essays of Warren Buffett, Benjamin Graham's The Intelligent Investor, etc.) that reinforced some of the principles of Greenblatt's Magic Formula.
I knew enough about the boom in commodities to be sure to include some of the handful of commodity companies that appeared on the list, but also included companies in other sectors. Aside from the commodity companies, all of which did well, and a couple of small cash-rich drug companies that were bought out for modest premiums, virtually every other stock in the portfolio plummeted. Judging from the lamentations on Yahoo! Finance's Magic Formula Investing Message Group, this has been a common experience.
In fairness to Joel Greenblatt, he did warn in his book that his Magic Formula system (like any mechanical system) wouldn't work all the time, and could under-perform the market for a few years in a row. In the book (pp. 71-73), Greenblatt also alluded to the hot-cold-hot roller coaster performance of O'Shaughnessy's screens in the 1990s, and to a period of under-performance experienced by his friend and fellow money manager Richard Pzena (neither O'Shaughnessy nor Pzena is mentioned by name in the book, but their identities are fairly clear from the descriptions). Nevertheless, the jaw-dropping Magic Formula losses last year (in what was, admittedly, an awful year for most broad-based value strategies) contrasted sharply with the back-tested performance of the Magic Formula system in Greenblatt's book. Over a 17-year testing period, the all-cap portfolio (with a minimum market cap of $1 million) only had one down year (the bear market year of 2002), and that year it merely had a single-digit loss.
After analyzing some of my losers, and see what some successful investors did differently, the lessons I took away were the importance of paying attention to the relevant macro trends, and that in a market when most stocks and most sectors are performing poorly, excessive diversification can be a liability.