The most preposterous quote I've heard in a long time

This is the most preposterous quote I've ever heard in a very, very long time:

In a recent survey of virgins 15 to 19, only 10 percent of boys and 7 percent of girls cited fear of disease as a reason not to have sex, Liddon said.

Say again? How exactly did they find virgins 15 to 19 years old?