A 1981 case study reported that stimulation of the anterior vaginal wall made the area grow by fifty percent and that self-reported levels of arousal/orgasm were deeper when the G-spot was stimulated. Another study, in 1983, examined eleven women by palpating the entire vagina in a clockwise fashion, and reported a specific response to stimulation of the anterior vaginal wall in four of the women, concluding that the area is the G-spot. In a 1990 study, an anonymous questionnaire was distributed to 2,350 professional women in the United States and Canada with a subsequent 55% return rate. Of these respondents, 40% reported having a fluid release (ejaculation) at the moment of orgasm, and 82% of the women who reported the sensitive area (Gräfenberg spot) also reported ejaculation with their orgasms. Several variables were associated with this perceived existence of female ejaculation.