General Discussion

You arrest somebody coming across the border and chuck them back out, they're deported.

You arrest somebody in Wichita and chuck back out, they're deported.

When there's relatively rates of high border crossing, deportation numbers can be very high (or not, depending if you chuck them back out). But if you don't wait for them to come to you, but have to go after them, each deportation costs a lot more in staff time: find them, detain them, house them, arrange for deportation.

A corollary went something like this: 15 years ago, a much larger proportion of illegal border crossings were Mexicans from Mexico, and both with adults and children it's easy to return them to their country of origin. But if they're Venezuelans and cross the Mexico-US border after living in Peru for 5 years, if they're Haitians or Dominicans (the nationality, not the order) returning them to Mexico--esp. in the case of minors--becomes both legally more difficult and, with minors, flat out illegal.

So there's an argument to be made that the decrease isn't driven by Trump-related temporary policy but structural in nature.

I heard something to that effect, so it must be true.