Comprehensive Fundamental Factor?

Is there a single variable based on accounting data that reliably captures expected returns of individual stocks? In their October 2018 paper entitled “A Fundamental Factor Model”, Stephen Penman and Julie Zhu construct and test a fundamental expected returns factor based on array of accounting inputs, encompassing earnings, book value and items that sum to these income statement and balance sheet totals. They focus on a robust version of this factor incorporating eight of these inputs (ER8), but consider simpler versions relying on only four (ER4) or two (ER2) inputs. They calculate a premium based on a portfolio that is each month long (short) the equally weighted stocks of firms ranked in the top (bottom) three tenths, or deciles, of the fundamental factor. They update fundamentals yearly three months after firm fiscal year ends from numbers published in annual financial statements. In terms of smart beta terminology, their approach replaces market capitalization weights with fundamentals weights. Using monthly returns and annual financial statements for a broad sample of non-financial U.S. common stocks during April 1981 (or June 1975 or April 1966 for simplified factors) through December 2015, they find that:

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