Selectivity, market timing, and random beta behavior of mutual funds: a generalized model

This paper presents a generalized varying parameter model to investigate the performance of mutual funds. The model allows beta nonstationarity to include both market timing and random beta behavior; therefore, it can be regarded as a general case of previous research. Forty‐three funds with a wide range of objectives are examined. The generalized varying parameter results indicate that about 30 percent of the funds show selectivity, 19 percent have random betas, and 14 percent indicate significant, yet negative, market timing performance. Therefore, mutual funds, as a group, show no market timing ability. The apparent ability to select undervalued securities, however, seems to conflict with the efficient markets hypothesis.