In 2005, Khytam Dawood and co-workers reported in the journal Twin Research and Human Genetics an anonymous survey of 3080 women, many drawn from the Australian Twin Registry, which included both monozygotic (so-called indentical) twins and dizygotic (fraternal) twins. These women were asked to report their frequency of orgasm from 3 types of sexual activity: intercourse with a partner, sex with a partner not involving intercourse and masturbation. 23% of women reported that they "always or almost always" achieved orgasm during sexual intercourse, 27% with partner sex other than intercourse and 38% during masturbation.
When twins, sibs and singletons were compared, this yielded an estimate of the genetic contribution to the variance in the frequency of orgasm: 31% genetic contribution for intercourse, 37% for non-intercourse partner sex and 51% for masturbation. To put this in perspective, genetic influences account for about 82 % of the variation in human height and about 80% of the variation in human body mass index. So, the genetic influences on women's orgasm frequency in this population are significant, but not overwhelming. It would be interesting to see this type of study repeated in other populations and cultural groups.