The broadest historical trends in voter turnout in the United States presidential elections have been determined by the gradual expansion of voting rights from the initial restriction to white property owners in the early years of the country's independence, to all citizens aged 18 or older in most of the last century. Voter turnout in the presidential elections has historically been better than the turnout for midterm elections.
Women's suffrage and gender gap
There was no systematic collection of voter turnout data by gender at a national level before 1964, but smaller local studies indicate a low turnout among female voters in the years following Women's suffrage in the United States. For example, a 1924 study of voting turnout in Chicago found that "female Chicagoans were far less likely to have visited the polls on Election Day than were men in both the 1920 presidential election (46% vs. 75%) and the 1923 mayoral contest (35% vs. 63%)." The study compared reasons given by male and female non-voters, and found that female non-voters were more likely to cite general indifference to politics and ignorance or timidity regarding elections than male non-voters, and that female voters were less likely to cite fear of loss of business or wages. Most significantly, however, 11% of female non-voters in the survey cited a "Disbelief in woman's voting" as the reason they did not vote.
The graph of voter turnout percentages shows a dramatic decline in turnout over the first two decades of the twentieth century, ending in 1920, when the Nineteenth Amendment to the United States Constitution granted women the right to vote across the United States. But in the preceding decades, several states had passed laws supporting women's suffrage. Women were granted the right to vote in Wyoming in 1869, before the territory had become a full state in the union. In 1889, when the Wyoming constitution was drafted in preparation for statehood, it included women's suffrage. Thus Wyoming was also the first full state to grant women the right to vote. In 1893, Colorado was the first state to amend an existing constitution in order to grant women the right to vote, and several other states followed, including Utah and Idaho in 1896, Washington State in 1910, California in 1911, Oregon, Kansas, and Arizona in 1912, Alaska and Illinois in 1913, Montana and Nevada in 1914, New York in 1917; Michigan, South Dakota, and Oklahoma in 1918. Each of these suffrage laws expanded the body of eligible voters, and because women were less likely to vote than men, each of these expansions created a decline in voter turnout rates, culminating with the extremely low turnouts in the 1920 and 1924 elections after the passage of the Nineteenth Amendment.
This voting gender gap waned throughout the middle decades of the twentieth century, and in recent decades has completely reversed, with a higher proportion of women voting than men in each of the last nine presidential elections. The Center for American Women and Politics summarizes how this trend can be measured differently both in terms of proportion of voters to non-voters, and in terms of the bulk number of votes cast. "In every presidential election since 1980, the proportion of eligible female adults who voted has exceeded the proportion of eligible male adults who voted [...]. In all presidential elections prior to 1980, the voter turnout rate for women was lower than the rate for men. The number of female voters has exceeded the number of male voters in every presidential election since 1964" This gender gap has been a determining factor in several recent presidential elections, as women have been consistently about 15% more likely to support the candidate of the Democratic Party than the Republican candidate in each election since 1996.
Race, ethnicity, and voter turnout
The passage of the Fifteenth Amendment to the United States Constitution gave black men the right to vote. While this historic expansion of rights resulted in significant increases in the eligible voting population, and may have contributed to the increases in the proportion of votes cast for president as a percentage of the total population during the 1870s, there does not seem to have been a significant long-term increase in the percentage of eligible voters who turn out for the poll. The disenfranchisement of most African Americans and many poor whites in the South during the years 1890-1910 likely contributed to the decline in overall voter turnout percentages during those years visible in the chart at the top of the article. Ethnicity has had an effect on voter turnout in recent years as well, with data from recent elections such as 2008 showing much lower turnout among people identifying as Hispanic or Asian ethnicity than other voters (see chart to the right).
Youth voting turnout
Recent decades have seen increasing concern over the fact that youth voting turnout is consistently lower than turnout among older generations. Several programs to increase the rates of voting among young people—such as MTV's "Rock the Vote" (founded in 1990) and the "Vote or Die" initiative (starting in 2012)—may have marginally increased turnouts of those between the ages of 18 and 25 to vote. However, the Stanford Social Innovation Review found no evidence of a decline in youth voter turnout. In fact, they argue that "Millennials are turning out at similar rates to the previous two generations when they face their first elections."
Other eligibility factors
Income and educational attainment are significant factors affecting voter turnout. Educational Attainment is perhaps the best predictor of voter turnout, and in the 2008 election those holding advanced degrees were three times more likely to vote than those with less than high school education. Income correlated well with likelihood of voting as well, although this may be because of a correlation between income and educational attainment, rather than a direct effect of income.
Another factor influencing statistics on voter turnout is the percentage of the country's voting-age population who are ineligible to vote due to non-citizen status or prior felony convictions. In a 2001 article in the American Political Science Review, Michael McDonald and Samuel Popkin argued, that at least in the United States, voter turnout since 1972 has not actually declined when calculated for those eligible to vote, what they term the voting-eligible population. In 1972, noncitizens and ineligible felons (depending on state law) constituted about 2% of the voting-age population. By 2004, ineligible voters constituted nearly 10%. Ineligible voters are not evenly distributed across the country – 20% of California's voting-age population is ineligible to vote – which confounds comparisons of states.
Note: The Bipartisan Policy Center has stated that turnout for 2012 was 57.5 percent of the eligible voters, which they claim was a decline from 2008. They estimate that as a percent of eligible voters, turn out was: 2000, 54.2%; in 2004 60.4%; 2008 62.3%; and 2012 57.5%. These were the same figures as given by the Center for the Study of the American Electorate.
Later analysis by the University of California, Santa Barbara's American Presidency Project found that there were 235,248,000 people of voting age in the United States in the 2012 election, resulting in 2012 voting age population (VAP) turnout of 54.9%. The total increase in VAP between 2008 and 2012 (5,300,000) was the smallest increase since 1964, bucking the modern average of 9,000,000-13,000,000 per cycle.