As of Oct. 31, more than 22 million Americans have already participated in early voting, the New York Times reported. Reuters

Millions of people have already made their decision between Republican Donald Trump and Democrat Hillary Clinton by voting early, and millions more will head to the polls for Election Day Tuesday.

But voter turnout in the U.S. is and has consistently been poor when compared to other democratic countries with free elections for a number of reasons. They include age, race, gender, felony convictions and incarceration, as well as views on how competitive the election actually is and thus how much a vote will count, according to an analysis by FairVote.org.

Younger voters, between 18-to-29 and from 1972 to 2012, have generally turned out 15 to 20 points less than eligible voters over the age of 30. Race played a significant factor in 2012 when President Barack Obama won his second term, when black voters beat out whites 66.2 percent to 64.1 percent, respectively. Latinos clocked in at 48 percent and Asians 47.3 percent.

Women, with the exception of those over the age of 75, have also outpaced men at the polls in every presidential election since 1980. But 72.2 percent of men 75 and older voted in 2012 compared to 64.9 percent of women in the same demographic.

In 2012, only 129.1 million voters cast a ballot compared to almost 241 million eligible voters, or 53.6 percent, ElectionProject.org found.

That puts the U.S. well behind a number of developed countries that employ free elections, including Belgium (87.2 percent turnout in 2014), Turkey (84.3 percent in 2015), Sweden (82.6 percent in 2014), South Korea (80.4 percent in 2012) and among many others, according to Pew Research Center.

The U.S. ranked No. 31 out of 35 countries that make the Organization for Economic Cooperation and Development.

Past felony offenses and those currently incarcerated also hold back turnout. In 2012, 1.4 million potential voters were in prison and more than 3.3 million were ineligible due to felony convictions, however, the Prison Policy Initiative estimated in March that there are more than 2.3 million people presently in the entire U.S. prison system.

Pessimism about this year’s election and the divisive candidates, however, may cause a record turnout. In fact, for the first time in U.S. history more than 200 million people have registered as of Oct. 19, according to Politico.