On second read, maybe that's not what you're saying, and I missunderstood. Forgive me--I haven't slept in 40 hours. :-)
Have you read, or read of, any of these longitudinal studies?: http://www.hoagiesgifted.org/eric/faq/gt-long.html
The best known longitudinal studies were conducted by Louis Terman. In 1921 Terman and his colleagues began a longitudinal study of 1,528 gifted youth with IQs greater than 140 who were approximately 12 years old. Over a period of approximately 40 years, the researchers laid the groundwork for our understanding of giftedness and paved the way for efforts to identify and nurture giftedness in school. Terman died in 1959 but the study will continue until 2020, to encompass the entire lives of his original 1528 gifted youth. Results of the study have been published in several volumes
http://books.google.com/books?id=KQ4rLiAbHQQC&pg=PA41...
Intelligence is an important determinant of lifetime achivement. The classical study demonstrating this association was carried out by Lewis Terman and his colleagues. The study began around 1920 by intelligence testing a large number of children in California. From this sample they selected 1,528 (857 boys and 671 girls) with IQs of 135 and above. The minimum IQ of 135 represents approximately the top one percent of the population. The average IQ of the total sample was 151 (Terman, 1925).
These children were followed up thirty-five years after their initial identification when they were in their early forties. By this time, the authors of the follow-up concluded that "the superior child, with few exceptions, becomes the able adult, superior in nearly every respect to the generality" (Terman and Oden, 1959, p. 143).
Terman and his associated found that 70 percent of their sample had graduated from college; two fifths of the men and three fifths of the women had gone through graduate school. Of the men, 86 percent were in the two highest socioeconomic categories of professions and management. None of these individuals were in the lowest socioeconomic category of unskilled workers, as compared with 13 percent of the male population at that time. Seventy of the men were listed in American Men of Science, and three had been elected to the National Academy of Sciences. Thirty-one were listed in Who's Who in America. Between them, they had produced nearly 2000 scientific papers, some 60 books in the sciences, 230 patents, and 33 novels. Fourteen percent of the men did not fulfill the promise of their high IQs and failed to obtain socioeconomic class one or two occupations. These men were almost all impaired by psychiatric problems or lack of motivation.
Among the women, most of them became housewives and mothers and consequently did not have such visible achievements. Nevertheless, seven women were listed in American Men of Science and two in Who's Who in America. Between them they had produced 32 scholarly books, 5 novels, more than 200 scientific papers, and 5 patents.
The other possibility is that I am completely wrong...
What I said in the other branch of this thread is that you'll never know if you can be great unless you spend your life trying, and that so few people do try that almost all of the people who really strive for it end up succeeding, to at least some degree.