The Wikipedia entry (https://en.wikipedia.org/wiki/Hymen) suggests that Hymen can be completed absent inborn. I read through the textbook referred by Wikipedia, but that textbook does not include any data on this; the textbook also made this claim without any reference to experimental observations or medical cases. How could an academic textbook claim something without valid data or evidence?
My question is, what is the approximate percentage of women born without hymen?