Furthermore it’s a pretty safe guess that the statistics are worse than that. Because if it’s a volunteer sample, the women most likely to come forward and be candid about sex are likely to be those who are also successful with sex. And while many people might be tempted to pretend they do orgasm when they don’t, few are likely to pretend that they don’t when they do. That’s about as probable as a woman claiming she weighs ten stone when she actually weighs nine. (Rachel Swift)