Fama and French conclude that the relationship between average return and beta is weak over the period from 1941 to 1990 and virtually nonexistent from 1963 to 1990. Why the relationship between average return and beta is weak? They also argue that the average return on a security is negatively related to both the firm's price-earnings (P/E) ratio and the firm's market-to-book (M/B) ratio. What is the meaning of that negative relationship?