The incidence of endometriosis is not known, since the only reliable way of determining its presence is through surgery or at autopsy.
Surgical incidence is biased by the selection process bringing the patient to the operating room.
No large cadaver study examining autopsy specimens for endometriosis has reported data that has been widely accepted. This increase was not fully accounted for by an increase in hysterectomies in general and occurred during a time when increasingly conservative management for endometriosis became popular.