About 3.8% of Americans identify as gay, lesbian, bisexual, or transgender. Yet Gallup found that Americans believe 23% of the population is gay or lesbian. You heard that right. Americans overestimate the number
of gay an lesbian people by a magnitude of more than six! So why do Americans think the number is 23% instead of 3.8%?
The reason is likely because the media tends to cover certain issues like gays and lesbians so much that people mistakenly believe there are many more gays and lesbians than there actually are. It's the same reason that more than half of Americans think gun violence has been rising, when in fact it's fallen 75% since 1993. The news mentions gun violence so much that people think it must be increasing. All this goes to show the power of the media to shape (or misshape) our views.
NOTE: Keep in mind that the tendency to hide ones sexual preference means the 3.8% number is likely on the low side of reality. Still, the stigma associated with being LGBT has decreased significantly, making recent polls that ask people for their sexual preference much more accurate than in the past.