A big reason for polarization in the United States is that we sort ourselves politically. The places we live, the news outlets we consume and the people we associate with tend to reinforce our political beliefs. That can create bubbles in which it's difficult to empathize with people who don't share our experiences and points of view.

And despite younger Americans being much more diverse and much more connected than older ones, these divides are still very real.

A new poll from the Harvard Institute of Politics asked whether adults younger than 30 had certain kinds of friends: Hillary Clinton supporters, Trump supporters, gun owners, members of the LGBTQ community, etc.

Some of the more interesting findings:

  • Just 39 percent of young Democrats have a close relationship with someone who supports Trump, while 55 percent of young Republicans know a Clinton supporter well.
  • More young Republicans know a millionaire (28 percent) than a Muslim (22 percent).
  • Just 26 percent of young Democrats know a veteran of the Iraq or Afghanistan wars, while 43 percent of young Republicans do.
  • While 73 percent of young whites know someone who owns a gun, just 41 percent of young Hispanics do (the number is 48 percent for young African Americans).
  • Just 49 percent of young Democrats know a gun owner, as opposed to 80 percent of young Republicans.
  • Just 27 percent of young African Americans know a police officer, compared with 40 percent of young whites.
  • Although 53 percent of young Hispanics know an undocumented immigrant, just 10 percent of young whites and 14 percent of young blacks can say the same.

Some of these numbers are perhaps a little less surprising than you might think. There are actually more millionaires in the United States (about 3 percent of the population) than there are Muslims (1 percent), for example. But millionaires tend to be senior citizens, for obvious reasons; only about 3 percent of millionaires are between the ages of 18 and 35, according to a 2012 Tax Foundation study, while 80 percent were over the age of 45. In contrast, about 6 in 10 Muslim adults are between ages the ages of 18 and 39. (Of course, people can also be closer with people who are older than them.)

Interestingly, the 61 percent of young Democrats who say they don't know a Trump supporter well is actually a bigger slice than among the overall population, according to a Pew Research Center poll last year.

That survey showed that 47 percent of Clinton backers didn't have any close friends who supported Trump. Again, Republicans had a more politically diverse group of friends, with 31 percent saying they had no Clinton-supporting close friends.

The questions were somewhat different — Harvard's “close relationship” vs. Pew's “close friend” — and Pew offered more options, which may have led to more middle-ground responses in its poll. But the gist is similar, and so are the partisan differences.

And the two polls side by side suggest that this is hardly a problem only among older Americans.