Weak and Semi-Strong Form Stock Return Predictability, Revisited
This paper makes indirect inference about the time-variation in expected stock returns by comparing unconditional sample variances to estimates of expected conditional variances. The evidence reveals more predictability as more information is used, and no evidence that predictability has diminished in recent years. Semi-strong form evidence suggests that time-variation in expected returns remains economically important.
Ferson, Wayne E., Andrea Heuson and Tie Su. "Weak and Semi-strong Form Stock Return Predictability Revisited." Management Science 51 (2005): 1582-1592.