The FEC considers three variables in its analysis of voter registration and turnout trends. The FEC calculates the VAP by state, as reported by the Census Bureau . The number is higher than the number of people who are actually eligible to vote, because voting age population includes non-citizens and others who, for various reasons, are ineligible to vote. In addition to natural population growth, three constitutional amendments between 1960 and 1971, and the 1965 Voting Rights Act, have substantially increased the voting age population.
Registration is the number of registered voters.
The FEC calculates the national registration total as reported by individual states and the District of Columbia. Turnout is the number of people who actually vote in a given election. The number is sometimes under-stated because it reflects only the number of people who vote for the highest office on the ballot. In other words, if an individual votes for a congressional, but not presidential, candidate, his vote is not included in the turnout calculation. The inter-relationship between these variables can be deceptive.