Because of the magnitude, persistence, pervasiveness and robustness of their related premiums, several factors have dominated the academic literature. Among them are market beta, size, value, momentum and profitability. However, despite their persistence, each factor has undergone even fairly long periods during which it produced negative returns.
Said another way, while investors can raise expected returns by increasing their exposure to the market, size, value and profitability premiums, over any given time period—no matter how long—the realized premiums can be negative. And that fact is what’s tempted many to find a way to “time the premiums”—to tactically allocate by shifting from stocks to bonds, small-caps to large-caps, value to growth and so on.
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