Less than half of eligible Latino voters nationally will vote in the 2016 presidential elections, according to an analysis released this week by a nonpartisan Latino group.

The analysis, conducted by the National Association of Latino Elected and Appointed Officials, predicts a 17 percent increase in the number of Latinos who will vote in 2016, compared with 2012.

But while NALEO expects 13.1 million Latinos to vote, the group says 27.3 million Latinos are eligible voters -- meaning Latinos face a massive voter participation gap.

"This really demonstrates one of the most significant challenges" for Latinos in the United States, said Eduardo Gamarra, a professor of Latin American politics at Florida International University.

Low voter turnout among 18- to 35-year-old Latinos is a major cause of the voter participation gap. About 44 percent of eligible Latino voters are millennials, according to a recent study by the Pew Research Center. But in 2012, a mere 37.8 percent of Latino millennials voted.

Gamarra said it's possible that turnout among Latino millennials will be similarly low this year. Older Latinos tend to place high importance on voting, since many of them fled Latin American and Carribbean regimes in order to attain political freedom. Being able to exercise the right to vote is important to them.

But Latino millennials tend to be more apathetic, Gamarra said. He said he thinks that's because young Latinos have assimilated with non-Latino millennials -- who also tend to not vote.

"We have a problem with young people voting generally in this country," Gamarra said. Latino millennials are "behaving increasingly like [non-Latino] American kids."

Their lack of interest could limit the political power of Latinos as a group. For the next two decades, millennials will be the main drivers of growth in the Hispanic electorate, according to the Pew study. About 3.2 million of them turned 18 and became eligible to vote between 2012 and 2016. But if they don't exercise that right, they won't have a say on issues like immigration, naturalization and U.S.-Cuba relations.

"Unless you get this young group to register and exercise their right to vote, they're not going to be that great promise that everybody thinks," Gamarra said.

Still, the NALEO analysis doesn't factor in the possible effects of voter registration drives or other efforts to register Latinos. Gamarra said that if such efforts are successful, the number of Latino voters -- of all ages -- who participate in the presidential elections will increase.

"The potential to be really important in elections is there," he said.