http://www.infoplease.com/ipa/A0781453.html
    Turnout of voting-age population (percent)

Year   Voting-age population Voter registration Voter Percentage
2008* 231,229,580                132,618,580*   56.8%
2006   220,600,000                135,889,600    37.1%
2004   221,256,931                174,800,000    55.3
2002   215,473,000                150,990,598    37.0
2000   205,815,000                156,421,311    51.3
1998   200,929,000                141,850,558    36.4
1996   196,511,000                146,211,960    49.1
1994   193,650,000                130,292,822    38.8
1992   189,529,000                133,821,178    55.1
1990   185,812,000                121,105,630    36.5
1988   182,778,000                126,379,628    50.1
1986   178,566,000                118,399,98    36.4
1984   174,466,000                124,150,614    53.1
1982   169,938,000                110,671,225    39.8
1980   164,597,000                113,043,734    52.6
1978   158,373,000                103,291,265    37.2
1976   152,309,190                105,037,986    53.6
1974   146,336,000                  96,199,0201   38.2
1972   140,776,000                  97,328,541    55.2
1970   124,498,000                  82,496,7472   46.6
1968   120,328,186                  81,658,180    60.8
1966   116,132,000                  76,288,2833   48.4
1964   114,090,000                  73,715,818    61.9
1962   112,423,000                  65,393,7514   47.3
1960   109,159,000                  64,833,0965   63.1