Gauquelin's work was accepted by the psychologist Hans Eysenck among others but later attempts to validate the data and replicate the effect have produced uneven results, chiefly owing to disagreements over the selection and analysis of the data set. Since the phenomenon in question depends upon the daily rotation of the Earth, the availability and accuracy of time and place of birth data is crucial to such studies, as is the criterion of "eminence". Later research claims to explain the Mars effect by selection bias, favouring champions who were born in a "key sector" of Mars and rejecting those who were not from the sample.