Across the World, Where Are the Voters?

Thanks to the 26th Amendment, which lowered the voting age from 21 to 18, some 11 million U.S. citizens have the right to vote today who otherwise wouldn't.

The amendment effectively granted the youth population the power to swing U.S. elections; voters between 18- to 24-years-old comprise about 15 percent of all eligible voters in the U.S., according to the United States Census Bureau. But in the 45 years since the amendment's passage in 1971, young voters have failed to represent themselves proportionately at the polls.

When it comes to voter participation, "The U.S. has the largest gap between ages out of the whole democratic world," says Paul Beck, co-director of the Comparative National Elections Project at The Ohio State University.

Before blaming it on the ignorance of youth and millennial narcissism, consider this: only 62 percent of U.S. citizens cast their ballot in the 2012 general election, according to the Census. The average voter turnout in all presidential and parliamentary elections across the globe since 2010 is 66 percent, according to the International Institute for Democracy and Electoral Assistance (IDEA). And voter participation in the U.S. tends to drop by a third in midterm elections, when the presidential post isn't at stake, Beck says.

In the 2014 U.S. midterm election, only 42 percent of voters came out to the polls. According to IDEA, that's just 7 percentage points higher than turnout among U.K. citizens in the same year to vote for European Union parliament, a group that the nation recently voted to leave and that many citizens seem to be generally confused about.

While voter participation rates in the U.S. are some of the lowest in the world, especially among the younger population and minority groups, the U.S. isn't the only country struggling to mobilize its voters. Established democracies around the world have seen a steady decline in attendance at the polls, especially since the 1990s.

In an historic referendum in June, U.K. citizens voted to leave the European Union. But those voters largely driving the decision won't have to live with the consequences as long as others. At 72 percent, voter turnout for those between 35 and 44 years old was double that of voters between 18 and 24 years old, according to polls by the British Sky News. That turnout rate only increased as voters grew older.

[READ: What is Brexit? Five charts explain the EU Referendum.]

"What drives people to the polls is the issue at stake," says Abdurashid Solijonov, a program officer for electoral processes at IDEA. Those issues seem more urgent in new democracies than established democracies.

To illustrate the contrasts between the attitudes of voters in new versus established democracies, Beck cites the Comparative National Elections Project's survey of German voters in the 1990 election. It was the first free election to combine both East and West Germany since the Communist rule of the East during the Cold War.

"Easterners were genuinely excited. There was high turnout," he says. "Westerners were thinking, 'This is just another election' and had an almost ho-hum attitude."

Trends were similar in post-communist Europe. As the public enjoyed the early years of "open and competitive elections," voter turnout was high, regularly around 80 percent in former communist countries like Bulgaria, the Czech Republic and Romania, according to an article in The Journal of Politics. But before two decades had passed, voter turnout had dropped to around 50 percent.

Besides countries like Australia and Singapore where voting is mandatory, the countries that report significant voter turnout rates are ones like Afghanistan (84 percent for the nation's first presidential election in 2004) and Kenya (86 percent for 2013 presidential election), according to IDEA.

Government records are the only source of voter participation rates, which can raise questions about unusually high turnout numbers reported by countries with a history of autocracy and corruption.

But Afghanistan and Kenya are countries "where voting is viewed as critical to evolution of a democracy, where voting is viewed as essential, where it makes a difference and people believe that the only way their life is going to be better is if they vote in a government that will do that," says John Hardin Young, an election law attorney and adjunct professor of international election principles at William & Mary Law School.

Despite the global decline of voter turnout, the U.S. is still a special case. Difficult registration processes, long lines, inconvenient voting times and new voter identification laws have created an atmosphere that seems to discourage civic engagement, says Young.

"It's a modern poll tax on the working class," he says.

When it comes to mobilizing voters, informal networks -- like friends, colleagues and neighbors -- are much more influential than outreach efforts of political parties. "The mere frequency with which voters discuss politics within their social networks is, in itself, a good predictor of whether they will themselves vote," says Pedro Magalhães in the book "Voting in Old and New Democracies." Voting "rewards conformity" and appeals to desires to improve one's social approval, acknowledgment and reputation.

So, will voter participation rates increase in the future? Maybe, if politics takes a more positive tone globally, says Beck. But turnout rates are also greatly affected by the age structure of a country's population, and, he says, "if we have a more aged population, which is where we're headed, voter turnout rates should increase."

Deidre McPhillips is a data reporter at U.S. News. You can find her on Twitter or email her at dmcphillips@usnews.com.