Youth vote in the United States
The youth vote in the United States is a political term used to describe 18- to 24-year-olds and their voting habits. Many policy areas specifically affect the youth of the United States, such as education issues and the juvenile justice system. The general trend in voter turnout for American elections has been decreasing for all age groups, but "young people's participation has taken the biggest nosedive". This low youth turnout is part of the generational trend of voting activity. Young people have the lowest turnout, though as the individual ages, turnout increases to a peak at the age of 50 and then falls again. 
Ever since 18-year-olds were given the right to vote in 1972, youth have been under represented at the polls. In 1976, one of the first elections in which 18-year-olds were able to vote, 18-24 year-olds made up 18 percent of all eligible voters in America, but only 13 percent actually voted - an under-representation of one-third. In the next election in 1978, youth were under-represented by 50 percent. "Seven out of ten young people…did not vote in the 1996 presidential election… 20 percent below the general turnout". In 1998, out of the 13 percent of eligible youth voters in America, only five percent voted. During the competitive presidential race of 2000, 36 percent of youth turned out to vote and in 2004, the "banner year in the history of youth voting," 47 percent of the American youth voted. Recently, in the 2008 U.S. Presidential election, the number of youth voters tripled and even quadrupled in some states compared to the 2004 elections.
Voting age population
Voting age population (VAP) refers to the set of individuals that have reached the minimum voting age for a particular geographical or political unit. The presumption is that they are therefore generally eligible to vote, although other additional factors may cause them to be ineligible, such as lack of citizenship or a prior felony conviction. In estimating voter turnout the voting age population for a political unit is often used as the denominator for the number of individuals eligible to vote in a given election; this method has been shown to lose in accuracy when a larger percentage of the VAP is ineligible to vote. In the United States individuals become eligible to vote in political elections at age 18.