Analysis of information sources in references of the Wikipedia article "Voter turnout in United States presidential elections" in English language version.
Voting Age Population is typically calculated based on census data ('resident population [21 or 18] years and older'). Voting Eligible Population is an attempt to more precisely determine the size of the U.S. electorate, by counting only those Americans who have a legal right to vote. The estimates of noncitizen residents and disenfranchised felons have been carried out mostly by Professor Michael McDonald.