http://www.theguardian.com/society/2015/apr/05/10-per-cent-population-gay-alfred-kinsey-statistics

This is a summary of estimates of the gay populations, mainly in US and UK, starting with Kinsey's famous figure of 10%.

About 9 million Americans are LGBT, and about 1.2 million Britons. Far larger numbers claim to have had some homosexual experience in their lifetimes.

In other words, about 2 1/2% of Americans, and 1 1/2% of Britons. (since the figures are arrived at by different methods, they should not be directly compared).

http://www.pewresearch.org/fact-tank/2013/10/09/study-polls-may-underestimate-anti-gay-sentiment-and-size-of-gay-lesbian-population/

In the Direct Report treatment, 11% of the population reports that they do not consider themselves heterosexual (8% for men, 16% for women). In the Veiled Report treatment, this increases to 19% (15% for men, 22% for women).

http://www.nber.org/papers/w19508?utm_campaign=ntw&utm_medium=email&utm_source=ntw

Comparing the two methods shows sexuality-related questions receive biased responses even under current best practices, and, for many questions, the bias is substantial. The veiled method increased self-reports of non-heterosexual identity by 65% (p<0.05) and same-sex sexual experiences by 59%