Why Surplus Consumption In The Habit Model May Be Less Persistent Than You Think

In U.S. data, value stocks have higher expected excess returns and higher CAPM alphas than growth stocks. The authors find the external-habit model of Campbell and Cochrane (1999) can generate a value premium in both CAPM alpha and expected excess return so long as the persistence of the log surplus-consumption ratio is not too high. In contrast, Lettau and Wachter (2007) find that when the log surplus-consumption ratio is assumed to be highly persistent as in Campbell and Cochrane, the external-habit model generates a growth premium in expected excess return. However, the micro evidence favors a less persistent log surplus-consumption ratio.