Last Updated Feb 23, 2011 12:04 PM EST
Jim Davis of Dimensional Fund Advisors asked the question: Why do firms differ so much from one another in their book-to-market (BtM) ratios? (Stocks with low BtM ratios are growth stocks, and those with high BtM ratios are value stocks.) For example, the 20th and 80th percentiles of BtM ratios for New York Stock Exchange firms since 1926 have averaged approximately 0.53 and 1.84. Similar gaps have been seen in firms in other countries as well.
Davis considered three possible causes for variation in BtM ratios across firms.
- Low BtM stocks have lower expected returns.
- Low BtM stocks have higher expected growth rates for cash flows.
- The first two are at work.
Davis then turned to the question of expected growth rates: Do growth companies actually grow faster? The research clearly shows that growth companies are more profitable. For example, from 1964-2009, while the return on assets (ROA) of growth stocks was 9.3 percent, the ROA of value stocks was just 3.6. Davis then looked at the evidence on growth rates and found that while there's some reversion to mean, growth companies persistently grow faster than value firms. Three years after quintile formation, the extreme quintiles still have average growth rates more than five percentage points apart. As Davis put it: "Growth firms earn their name by growing faster, and the faster growth persists."
It seems logical that companies that tend to be more profitable and also tend to grow faster have less risky cash flows and thus their stocks are perceived as less risky. And risk-averse investors (like you) will demand a risk premium for owning the stocks of riskier companies.
Davis concluded that of the three possibilities he listed, the results support number 3. The evidence indicates that growth firms have low BtM ratios because they have both higher expected growth rates and lower expected returns.
I would add this. While the value premium has been 6.6 percent, the standard deviation of that premium has been 16.4 percent, or 148 percent of the premium. That's another sign that the value premium isn't a free lunch.
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