"We actually did commission data within the survey and asked about to what degree they were closeted," Gates said, "and 13 percent who identified as LGB had never told anyone about it."
The most interesting results, according to Gates, were the data on bisexuals, which made up about half of the overall LGB population. Of those who identified as such, 25 percent said they were closeted.
"Many are still quite discreet about their sexual orientation," he said. "If you ask people in the bisexual population, they will tell you it's a different kind of a stigma they experience. Some don't feel completely at home in the LG community because they often think of them as being way too gay and hold them with a level of suspicion. And in general, they are subject to the general stigma of same-sex behavior."
Gates also cautioned against the results that 11 percent of all Americans had same-sex attractions.
"That was only from one survey and it was restricted to 18- to 44-year-olds," he said.
Respondents had to rate their attraction from exclusive opposite-sex attraction (5) in graduating degrees of same-sex feelings (4 to 1).
"Some in category 4 may be people like me who avoid 1s and 5s in surveys," Gates said.
The U.S. Census does not count how many Americans identify as LGBT, although it will release later this year its count of same-sex spouses.
Richard Socarides, president of the gay advocacy group Equality Matters, said the Williams report is a good tool, but the government should be tracking LGBT Americans in the census.
When he served as special assistant to President Bill Clinton on LGBT policy issue, Socarides said, he urged the White House to "count gay people."
"They still won't do it, and now they are counting same-sex couples who live together, but that's not counting," he said. "Just as the census does a survey of race and ethnicity, they ought to do sexual orientation."
He praised the Williams Institute but said the latest study is "at best an educated guess."
"They take a bunch of surveys that are out there and made some judgment based on the available information," said Socarides.
What the results do show, Socarides said, is "absolute fluidity" in sexual orientation, "especially for young people who don't have the kind of stereotypes that adults do."
The impact of studies like these will be far reaching, according to Socarides.
"It's important first, because the country is in the middle of making important policy decisions about the rights of gay people and, in that context, it's important to know how many Americans are affected," he said. "Another reason for the government to know is funding issues tied to health and education.
"Now that sexual orientation has essentially come out of the closet and people are not so fearful," he added, "you'll see a greater willingness to count gay people and we really need reliable information."