how many factors do you have to compute? the low amount of "competition" in earlier times of the century as far as prominent media sex symbols go? the enormous amount of mediatic attention and coverage that certain female celebrities received at the peak of their youth?
like Bardot, she exhibited an amount of sexual inhibition that was nearly unheard of in her time, which garnered her worldwide fame
Anna Kournikova, got years of non-stop coverage of her tennis matches simply because of her looks, and had countless newspapers/magazine articles that constantly flaunted her image
two ladies responsible for the death of an infinity of spermatozoids