What percentage of americans live past 45 years old?
It is estimated that more than 55% of Americans live past 45 years old. However, the life expectancy is dependent on gender as women are known to live longer than men. Check out the links for additional details http://en.wikipedia.org/wiki/List_of_countries_by_life_expectancy and http://en.wikipedia.org/wiki/Life_expectancy.
Probably most, probably over 55%