It really depends on what terminology some studies use and how questions are asked (this is the issue with all statistics and surveys) Here is a data dump from articles I've researched:

This article of a self-reported online survey states that "Nearly 10% of males and 4% of females reported some likelihood of having sex with children or viewing child pornography."

In another psychological study via Amazon MTurk, 9% of men would watch child pornography if they wouldn't get caught, 6% would have sex with a child if they wouldn't get caught, and 4% agreed to the statement that "I am sexually attracted to little children; I fantasize about having sex with a child; I masturbate to fantasies about having sex with a child."

For women, those rates are similar but lower; 2% state they would have sex with a child if they wouldn't be caught.

In a peer-reviewed scientific journal study conducted at Kent State in 1995, 88% of men were sexually aroused when presented with pictures of female children under the age of 12. 95% were aroused when presented with pictures of female adults.

Most studies provide inconclusive numbers due to the taboo nature of the test subject in question, wordage of questions, etc. I've seen figures go as low as 0.1%, but after seeing so many results from surveys and tests, I'd say roughly 2% of people over the age of 18 are attracted to people under the age of 18 consistently enough to be deemed pedophilies/hebephilies/etc.