On election day we look back to the last national election day to measure the size of the voting population in the United States. Worth noting is the fact that 2010 is a congressional election year but not a presidential election year. Throughout our history, voter turnout has been higher in presidential election years than in midterm election years.

Geographic reference: United States
Year: 2008
Market size: Number of voting age citizens: 206.1 million
Market size: Number of registered voters: 146.3 million
Market size: Number of people who actually voted: 131.1 million or 63.7% of citizens of voting age and 89.7% of the registered voter population.
Source: “Voting and Registration in the Election of November 2008,” Current Population Reports, May 2010, available online here. This is a most interesting report, full of details about the voting age population in 2008, measured and assessed by a number of demographic aspects: age, educational attainment level, race, ethnicity, gender, etc.
Original source: U.S. Bureau of the Census