Just when we thought Alfred Kinsey was dead and buried, he turned up again, like a bad penny in the sex education curriculum of the Montgomery County, Md., public schools.

Kinsey makes a cameo appearance in this curriculum designed for use in eighth and 10th grades. According to a handout entitled, “Myths and Facts,” “Alfred C. Kinsey's landmark research beginning in the 1930s and continuing into the 1950s demonstrated that homosexual behavior occurs in this country much more frequently than people had imagined.”

Since we have no way of knowing how prevalent “people had imagined” homosexual behavior to be, this statement can't be disproved. But Kinsey's shadow hovers over the curriculum, in claims that have been disproved.

For instance, the curriculum informs the students:

“You probably don't know any who are ‘out’ to you, although a significant percentage of the population is gay, lesbian or bisexual (approximately 1 in 10). That represents approximately 60,0000 (sic) people in Edmonton.”

Overlook the fact that this work is so numerically illiterate with this misplaced comma that we can't be sure whether the curriculum is trying to say 60,000 or 600,000 people in Edmonton are homosexual.

Go to the more basic question: Where does that 10% figure come from? Political activists distilled from Kinsey's work the claim that 13% of men and 7% of women are homosexual. The advocates averaged these two numbers as part of a public relations campaign to convince the public that “gay people are everywhere.”

But Kinsey's numbers don't hold up. The most definitive debunking of Kinsey's work was done in the dispassionate University of Chicago study, The Social Organization of Sexuality, by Edward Laumann, John Gagnon, Robert Michael and Stuart Michaels, published in the 1990s. The section entitled “The Myth of 10% and the Kinsey Research” has harsh words about Kinsey's scientific method.

Kinsey's pool of study subjects “failed to meet even the most elementary requirements for drawing a truly representative sample of the population at large,” the study found.

The professor drew his interview subjects from groups of people especially likely to have had unusual sexual experiences. He recruited from prisons and reform schools, including men imprisoned for sex offenses. He recruited from homosexual friendships and acquaintance networks, thus inflating the estimated percentages of homosexual practice far above any other estimates based on representative sampling techniques.

This potential problem with Kinsey's sampling technique has been known since at least 1952, when the eminent humanist psychologist Abraham Maslow published a paper called, “Volunteer Error in the Kinsey Study.” No other study using a statistically representative sampling of the whole population has ever come close to replicating Kinsey's percentages.

The more general problem is that the concept of homosexuality is by no means clear-cut. How do we classify someone as homosexual or not homosexual? If we can't answer that question reliably, then “10% of the population is gay” is not a meaningful statement.

The University of Chicago study spent considerable effort on this question, and identified three conceptually distinct dimensions of homosexuality. Homosexuality can include same-sex behavior, same-sex attraction or self-identification as being homosexual. We can also differentiate among people predominantly attracted to and people occasionally attracted to same-sex partners.

Finally, having same-sex partners at one time in one's life does not necessarily mean the person will exclusively have same-sex partners throughout their lifetime.

Using these distinctions, Laumann and his co-authors found a core group of the population who define themselves as homosexual or bisexual, have same-gender partners and express same-sex desires. The size of this group is a very modest 2.4% for men and 1.3% for women. Nowhere near Kinsey's 10%, repeated by the Montgomery County sex ed curriculum.

The authors of the curriculum illustrate their confusion even further by making a statement that is actually true.

“Myth: A person is a homosexual if he or she has ever been sexually attracted to, or ever had sexual contact with someone of the same gender.

“Fact: Fleeting attraction or contact does not prove long-term sexual orientation.”

Very true. And a very sensible thing to mention to hormone-charged eighth and 10th graders who might jump to unwarranted conclusions about themselves.

The University of Chicago study asked about this very question of the persistence of same-sex behavior over the course of a lifetime. Even among people who have had some same-sex partners, few people have had exclusively same-sex partners throughout their lives.

For instance, 2% of men reported having exclusively had male partners in the last year, but a paltry .6% of men exclusively had male partners since puberty. While 1% of women exclusively had same-sex partners during the last year, only a microscopic .2% of women had exclusively female partners since puberty.

So while the Board of Education is to be congratulated for observing the unstable nature of same-sex attraction, their material is still misleading and inconsistent. The only way to come up with a figure of 10% of the population being homosexual is to include people who have only had fleeting same-sex attractions or contact.

If “gay” means someone who has a lifelong pattern of exclusively same-sex partners in the presence of available opposite-sex partners, the percentage of homosexual people in the general population is truly small, and certainly nowhere near Kinsey's 10%.

The U.S. District Court in Maryland threw out this sex education curriculum on religious freedom grounds, and did not examine the accuracy of the content. It is sure to be revised, to address the Court's objections.

Maybe the next revision will take a closer look at the facts about same-sex attraction and same-sex behavior, rather than simply parroting Kinsey's outdated, and incorrect, work.

Jennifer Roback Morse is a research fellow at the Hoover Institution.