The earliest serious attempt to ascertain the age of maximum sexual activity, and the effect of age on sexual performance in the human male, was made by R. Pearl in 1925. This has been termed a nicely analysed study by a biostatistician using hospital data on 257 older, married, white males, most of them over 55 years of age. They had all undergone prostatic operation. In particular, data from 213 men (average age 65.53 years) - who felt they could recall the frequencies of marital intercourse in their earlier histories - were analysed. The age of maximum sexual activity for this group was located in the 30-39 year period, a circumstance thought to have sociological (e.g. lack of opportunity) significance rather than physiological. On a limited empirical basis Pearla concluded that the peak of activity "is in the 20-29 decade and that thereafter there is a steady decline." The survey has been criticised on account of its neglect of education as an influential parameter in making rural and urban comparisons.