<P> According to the Centers for Disease Control in 2011, an estimated 1.2 million people were living with HIV / AIDS in the United States . </P> <Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (September 2011) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (September 2011) (Learn how and when to remove this template message) </Td> </Tr> <P> A study by William Strauss and Neil Howe, in their books Generations and Fourth Turning, looked at generational similarities and differences going back to the 15th century and concluded that over 80 - year spans, generations proceed through four stages of about 20 years each . </P>

What percentage of us population is over 18