The term is often used to apply to less serious sexual relationships between related people. It is difficult to say how frequent incest is, but researchers have estimated that between 10% and 15% of people have at least one "incest experience" (this means some kind of sexual relationship falling short of actual incest). Less than 2% of these involve intercourse or attempted intercourse. Among women, research by Russell (1986) and Wyatt (1985) has given estimates as high as twenty percent (for such 'incest experience'). In a survey of women in San Francisco, of those who had grown up with a stepfather, 17% (1 in 6) said that he sexually abused her. In the same study, 2.5% (1 in 40) of the women said that they had been sexually abused by their father. Cousincest refers to incest with a cousin. Siblingcest refers to incest with a sibling.