Oft quoted Dutch study of 700,000 men. Except that never actually happened. It was an extrapolation of the original 172 men from the Kirkemo study “QUESTIONNAIRE-BASED OUTCOMES STUDY OF NONONCOLOGICAL POST-VASECTOMY COMPLICATIONS”.
Amazingly if you extrapolate 10% from a small study, you get 10% of a big number as well. Luckily, only trashy places like Harvard Medical School and Massachusetts Hospital complete lost the point of this metastudy.