What We Know About the Syrian Refugees
A look at who the refugees are and what we can expect from those already here.
— -- As the debate heats up over whether states will accept Syrian refugees, Republican presidential candidates have doubled down on objections to allowing them asylum in the United States, expressing concern that terrorists may also slip in among the innocent civilians seeking to escape a 3-year-long civil war in their homeland.
From Ben Carson's making a comparison between some refugees and rabid dogs to Donald Trump's saying he would ban all Syrian refugees, the debate has only intensified, with more than 30 state governors saying they oppose having Syrian refugees in their state.
Here is a look at who the refugees are and what we can expect from those already here.
Who are the Syrian refugees?
Overall, more than 4 million Syrians have registered with the United Nations refugee agency. Of those, nearly 40 percent are children under the age of 11, according to the agency. Overall, 76 percent of all registered refugees are women and children.
Just over 2,100 Syrian refugees have been resettled in the U.S. since Jan. 1, 2012, according to the State Department's Bureau of Population, Refugees and Migration.
Senior Obama administration officials explained on a background call with reporters earlier this week: "Half of the Syrian refugees brought to the U.S. so far have been children. A quarter are adults over 60. Only 2 percent are single males of combat age."
How Are They Checked?
Syrian refugees are subjected to "the most rigorous screening and security vetting of any category of people entering the United States," according to senior administration officials.
The process often takes one to three years to complete and includes biometric testing and intensive overseas interviews with Department of Homeland Security experts.
DHS officials told ABC News that refugees are subject to the highest level of security checks of any category of traveler to the United States, "including the involvement of the National Counterterrorism Center, the FBI's Terrorist Screening Center, the Department of Homeland Security, the Department of State and the Department of Defense. All refugees, including Syrians, are admitted only after successful completion of this stringent security screening regime."
How Many Refugees Will the U.S. Allow In?
Donald Trump has also asserted that President Obama wants to allow 250,000 Syrian refugees to come to the U.S. But the administration has in fact only agreed to allow 10,000 Syrian refugees in the next year.
Secretary of State John Kerry announced in September that the United States will increase the number of refugees admitted to the U.S. from across the world from 70,000 to 85,000 in 2016 and up to 100,000 in 2017.
Since the inception of the U.S. refugee program in mid-1970's (post-Vietnam), nearly 3 million refugees have been relocated to 180 locations in almost every state across the United States, to include almost every state, according to the State Department.
But Are They Dangerous?
Of the 497 individuals charged with "homegrown terrorism" in the United States between 2001 and August 2015, nine had refugee status, while the vast majority, 320, were U.S.-born citizens, according to data from New America, a nonprofit, non-partisan think tank based in Washington, D.C.
When looking at only terrorism classified as "jihadist," 80 percent were U.S. citizens at the time of the crime, but 50 percent were born in the U.S.
David Sterman, senior program associate at New America, explained that the group has not identified any Syrian-born actors in its data.
ABC News' Ben Siegel and Justin Fishel contributed to this report.