Often it is war and conflict. You mentioned also persecution.
So the way the Refugee Convention defines it is a well-founded fear of persecution. So you can have refugees who are targeted because, let's say, they're a member of a particular ethnic group or what we see, unfortunately, all around the world because they're gay and they're targeted just because of their sexual orientation.
So you can have refugees because of something about them that people choose to persecute. The people you tend to see fleeing Syria, of course, generally are fleeing conflict. But what unites them all is they have a sense of hopelessness and a sense of deep fear for themselves and for their families.