The clitoris: the whole iceberg
A study of 1,055 women ages 18-94 found that:
"18.4% of women reported that intercourse alone was sufficient for orgasm,
36.6% reported clitoral stimulation was necessary for orgasm during intercourse,
and an additional 36% indicated that, while clitoral stimulation was not needed, their orgasms feel better if their clitoris is stimulated during intercourse"
(Herbenick, D et al. 2015)