These are difficult stats to get because of the intense biases one way or the other. And apparently it has varied historically and is very dependent on cultures.
For example in pre-Christian Greece the percentages of homosexual men could have been as high as 80 to 90 % in Athens. Plato's Dialogs cite several instances of younger men being physically attracted towards Socrates, which must have been amusing. In the city state of Sparta homosexuality and pedophilia was government policy and men slept with boys for their pleasure as part of their military way of life.
After the Christianization of Greece probably in part from the puritanical attitudes of the early church leaders acting out the wishes of St. Paul, the percentages appear to have dropped significantly to whatever thay are today. This change in percentages must have occurred over hundreds of years.
Homosexuals tend to exagerate their percentages in American society. Ten percent is probably an exageration. It is most likely more like 3 to 4%. In the United States during the 2004 elections, exit polls indicated 4% of all voters self-identified as gay or lesbian. In some parts of the country it could be much less, and in cities like San Francisco it could actually be 20%. A recent study found 40% of single men in San Francisco were homosexual. The 2000 census in the USA indicated that about 0.99% of couples were same-sex. A survey in Canada indicated that only 1% of its population is homosexual. Homosexuality appears to be more common in Muslim societies.
This variation in percentages tends to indicate that there is an environmental factor to whether a person is homosexual or not. And the significant change in percentages of homosexuals in Greek society indicates that it is a behavior that can be altered, perhaps not in the individual, but over many generations as an acceptable mode of sexual expression. This indicates that there is a locking in of sexual orientation at some early age prior to puberty.
Percentages of lesbians appears to be lower than for homosexual men. One study indicated that only 0.32% of women were lesbians. But that study was from a religious organization and such organization are notorious about providing disinformation and outright lies about homosexuals. Unfortunately homosexual organizations tend to also provide disinformation in regards to their precentages and tend to exagerate their numbers with the hopes of achieving political influence.