Obtaining precise numbers on the demographics of sexual orientation is difficult for a variety of reasons, including the nature of the research questions. Most of the studies on sexual orientation rely on self-reported data, which may pose challenges to researchers because of the subject matter's sensitivity. Some studies examine self-reported data on same-sex sexual experiences, while other studies examine self-reported identification as homosexual, heterosexual or bisexual. Overall, fewer research subjects identify as homosexual or bisexual, than report having had sexual experiences or attraction to a person of the same sex. Survey type, questions and survey setting may affect the respondents' answers.