The first sentence:
According to the World Health Organization (WHO), the United States ranked 29th in the world in 2006 in life expectancy at age 50.
...is saying that America ranks 29th in the world for life expectancy, that being 50. Which isn't the case.
is saying that America ranks 29th in the world for life expectancy, that being 50. Which isn't the case.
The sentence says "life expectancy at age 50." In other words, life expectancy from 50 on.
I give up.