The fraternal birth order effect has been described by one of its proponents as "the most consistent biodemographic correlate of sexual orientation in men". In 1958, it was reported that homosexual men tend to have a greater number of older siblings (i.e., a 'later/higher birth order') than comparable heterosexual men and in 1962, these findings were published in detail. In 1996, Ray Blanchard and Anthony Bogaert claimed that the later birth order of homosexual men was solely due to a number of older brothers and not older sisters. They also found that each older brother increased the odds of homosexuality in a later-born brother by 33%. Later the same year, Blanchard and Bogaert reported the older brother effect in the Kinsey Interview Data, a "very large and historically significant data base". In a study published in 1998, Blanchard called this phenomenon the fraternal birth order effect.