How big is ISIS's following in the US? Here's what we know.

Impact

There's been a lot of panic in recent years about the threat of ISIS to the United States, from President-elect Donald Trump's infamous proposed ban on Muslims entering the U.S. to FBI Director James Comey 2015 allegation that there may be "thousands" of ISIS sympathizers inside the U.S. 

As attacks in Paris, Brussels and elsewhere have shown, ISIS does present a threat to the West — but are its ideologies as widespread in the U.S. as Republicans have claimed? While it's impossible to pinpoint an exact number of people who sympathize with ISIS, here's what we do know about the size of this deadly following.

Syrian travelers

The most high-profile ISIS recruits are those who travel to the Middle East — specifically Syria — to join the ISIS cause and develop new skills and ideas that they can bring back to the West. But while an estimated 6,900 ISIS recruits are thought to have traveled to Syria from Western countries (primarily in Europe) as of February 2016, only 250 have traveled to Syria, or attempted to travel there, from America.

A March 2016 study conducted by New America and the International Security Program, meanwhile, notes that 7 in 10 American foreign fighters are arrested before reaching Syria, with only 27 actually making it to the country. Only seven have returned from fighting, with one later returning to Syria and being killed in a suicide mission, according to the study, and only eight Americans who have traveled to Syria remain at large. NPR, however, offers a conflicting report, noting in 2015 that nearly three dozen fighters had returned. Whatever the number, though, this amount stands in sharp contrast to the thousands of jihadi fighters that have returned to Europe.

Homegrown sympathizers

Of course, many of those who sympathize with ISIS never make their way to the Middle East, and when taking these followers into account, the size of ISIS's U.S. following grows. A study from George Washington University's Program on Extremism reports that 71 individuals in the U.S. were charged in connection to ISIS-related activities between March 2014 and November 2015, while a June 2015 report from NPR counted nearly 60 cases in the U.S. that are linked to ISIS in some way. The Washington Post now puts the number at 106 men and women, as of November 2016. This, of course, does not account for the ISIS sympathizers who remain at large or have not yet made their beliefs known.

Of these 71 arrests noted by George Washington University, however, only 27% were involved in plots regarding attacks on U.S. soil; most were interested in doing harm overseas or supporting fighters in Syria and Iraq. And while much has been said by Republicans on the dangers of letting in refugees fleeing the country, the study also notes that 64 of the 71 arrested are U.S. citizens or permanent residents.

ISIS sympathizers also have a huge online presence, with one-fourth of the fighters in the GWU study having identified 300 active American or U.S.-based ISIS followers online. A 2014 study conducted by the Brookings Institution and Google Ideas, reported on by Mashable, found 46,000 Twitter accounts associated with ISIS. Many of these users are located in the Middle East, however, and the report also notes that many accounts may falsely list their locations as being within the United States in order to create the appearance of a larger threat.

A small percentage

While ISIS does present a real threat, in comparison to the larger Muslim population in the U.S., the numbers remain incredibly small. The Pew Research Center estimates there are 3.3 billion Muslims living in the U.S. as of 2015, meaning that the 107 charged for ISIS-related activities make up just a tiny fraction of the whole.