Expected returns can hardly be estimated from time series data. Therefore, many recent papers suggest investing in the global minimum variance portfolio. The weights of this portfolio are usually estimated by replacing the true return covariance matrix by its time series estimator. However,...

It seems to be widely accepted that Jensen alpha fails to detect successful market timing funds spuriously indicating poor fund performance. Jensen (1972), Admati and Ross (1985), Dybvig and Ross (1985), and Grinblatt and Titman (1989), (1995) attribute that to an upwards biased estimate of the...