Basic Types of Sexual  Behavior

3. Homosexual Intercourse

A Matter of Degree

There is, of course, nothing new or revolutionary about these categories as such. It has always been known that there are people who engage only in heterosexual intercourse, and that there are others who engage only in homosexual intercourse. It was also well understood that some individuals have intercourse with members of both sexes. However, before Kinsey’s large statistical studies, most “experts” simply assumed that the percentage of people with exclusively heterosexual histories was so great and the percentage of all others so small that any scale would have been hopelessly out of balance. In other words, homosexual acts were believed to be so rare as to represent nothing more than "unnatural" and freakish exceptions.
Kinsey showed that this traditional view was quite mistaken. For example, his statistics revealed that, by the time they reach middle age, about 50% of all males (and 20% of all females) have had some sort of overt erotic experience with members of their own sex. These numbers were later disputed, and other researchers arrived at much lower percentages. Nevertheless, Kinsey’s basic finding has stood the test of time: Heterosexuality and homosexuality are matters of degree:

Sexual Orientation Sexual orientation is defined as a person's heterosexuality or homosexuality. It is determined on the basis of preference for sexual partners.   People are heterosexual or homosexual to the degree in which they are erotically attracted to partners of the other or same sex. Most individuals develop a clear erotic preference for partners of the other sex (heterosexuality).   However, a minority are erotically attracted to both women and men (bisexuality), and an even smaller minority are attracted mainly to partners of their own sex (homosexuality).