Kinsey, Alfred, Pomeroy Wardell B., & Martin Clyde E.; Kinsey Report -- excerpted entries on homosexuality; Excerpts from a book
Excerpts from Kinsey et al's Sexual Behavior in the Human Male:
[Chapter 7: Age and Sexual Outlet, pp. 259-261] Homosexual activity and age.
[Chapter 8: Marital Status and Sexual Outlet, pp. 259-261]
[Chapter 10: Social Level and Sexual Outlet] - [sub-heading: Incidences and Frequencies of Sexual Outlet, pp. 357-362] & [sub-heading: Patterns of Behavior, pp. 383-384]
[Chapter 12: Rural-Urban Background and Sexual Outlet, pp. 455-459]

Kinsey, Alfred, Pomeroy Wardell B., & Martin Clyde E.; Sexual Behavior in the Human Male (Chapter 21 - HOMOSEXUAL OUTLET); 0-1
[...] Homosexual contacts account, therefore, for a rather small but still significant portion of the total outlet of the human male. [...]
If homosexual activity persists on as large a scale as it does, in the face of the very considerable public sentiment against it and in spite of the severity of the penalties that our Anglo-American culture has placed upon it through the centuries, there seems some reason for believing that such activity would appear in the histories of a much larger portion of the population if there were no social restraints.
[...]
The homosexual has been a significant part of human sexual activity ever since the dawn of history, primarily because it is an expression of capacities that are basic in the human animal.