The value spread as a predictor of returns

"Recent studies have used the value spread to predict aggregate stock returns to construct cash-flow betas that appear to explain the size and value anomalies. We show that two related variables, the book-to-market spread (the book-to-market of value stocks minus that of growth stocks) and the market-to-book spread (the market-to-book of growth stocks minus that of value stocks) predict returns in different directions and exhibit opposite cyclical variations. Most important, the value spread mixes information on the book-to-market and market-to-book spreads, and appears much less useful in predicting returns"--National Bureau of Economic Research web site.