I think there are a number of factors.
One of them is the sort of crackdown that has taken place, not only along the border with Mexico but, more importantly, on Mexico's border with Guatemala. At that level, the Mexican authorities, in cooperation with U.S. border officials, have been much more involved in apprehending and sending back individuals, migrants, to their countries of origin, which primarily have been Honduras, El Salvador, and Guatemala. Of course, Honduras has seen the highest rise in this migration.
I think Honduran officials at the border are also cooperating to a large degree, and being much more restrictive on the passage of individuals, particularly young children, across the border.
I'd like to highlight that this does pose some important issues for human rights defenders, who consider that in many cases these children are going back to extremely life-threatening situations. This is not being taken into account. As you may know, the United Nations High Commissioner for Refugees considers that a majority of the children who have been migrating north could in fact be considered for refugee status, but this is not a status that is being considered on a sort of broad basis at this time, by either the U.S. government or the Mexican government or neighbouring governments.