 | This article contains promotional content .(January 2025) |
Magic formula investing is an investment technique outlined by Joel Greenblatt that uses the principles of value investing.
| This article contains promotional content .(January 2025) |
Magic formula investing is an investment technique outlined by Joel Greenblatt that uses the principles of value investing.
Greenblatt (b. 1957), an American professional asset manager since the 1980s, suggests purchasing 30 "good companies": cheap stocks with a high earnings yield and a high return on capital. He describes this as a simplified version of the strategy employed by Warren Buffett and Charlie Munger of Berkshire Hathaway.
He touts the success of his magic formula in his book 'The Little Book that Beats the Market' ( ISBN 0-471-73306-7 published 2005, revised 2010), stating it averaged a 17-year annual return of 30.8%. [1]
He wrote the book for a non-technical reader (his teenaged children were the target audience), but an appendix includes more advanced explanations and data for readers with relevant experience or education. Greenblatt's system analyzed the largest companies trading on the American stock market, ranked by the largest 1,000, 2,500 or 3,000, for a 17 year period before the book's 2005 publication. Smaller companies, $50 million or under, were avoided because they tend to have fewer shares in circulation and large purchases can cause sharp changes in share prices. Greenblatt did not test this hypothesis on international stock markets due to difficulties comparing international and American data, but believed it would apply globally. He also stressed the formula will not necessarily be successful with any specific stock, but will be successful for a group of stocks as a unit or block.
He goes on to assigning numerical rankings, based on each company's earnings yield and return on capital:
"...a company that ranked 232nd best in return on capital and 153rd best in earnings yield would receive combined ranking of 385 (232 + 153). [...] Getting excellent rankings in both categories, (though not the top ranked in either) would be better under this ranking system than being the top-ranked in one category with only a pretty good ranking in the other."
From here, Greenblatt recommends selecting 20 to 30 of the better-ranked companies, selling them at predetermined intervals and replacing with new stocks that fit the formula.
Greenblatt's analysis found when applied to the largest 1,000 stocks the formula underperformed the market (defined as the S&P 500) for an average of five months out of each year. On an annual basis, the formula outperformed the market three out of four years but underperformed about 16% of two-year periods and 5% of three-year periods. Greenblatt asserts the formula out-performed market averages 100% of the time for any period longer than three years and worked best over three to five years or more. Results were even better and with lower risk when the formula was applied to larger pools of stocks like the largest 3,000 companies. The formula can thus be a contrarian investing strategy, focused sometimes on staying committed to stocks that might be temporarily unattractive or with sub-par performance.
In an afterword to the 2010 edition, Greenblatt admitted three possible flaws to the formula:
A number of studies have found merit in Greenblatt's "magic investing formula" in various markets around the world. However, the studies have also often noted increased volatility, short-term underperformance and other potential risks.
A 2024 study evaluates the formula for the U.S. market from 1963 to 2022 and compares it with the performance of the Piotroski F-Score, Acquirer's Multiple, and Conservative Formula. The study finds that all four formulas generate significant raw and risk-adjusted returns, primarily by providing efficient exposure to well-established style factors. However, no single formula consistently outperforms across all performance metrics. While the Acquirer's Multiple achieves the highest returns for top decile portfolios and the Conservative Formula leads in CAPM alpha and return spread, the Magic Formula exhibits the highest remaining alpha after adjusting for common factors. [12]