Migrant Crossings at US-Mexico Border Fall by Half in January; What's Next?

FILE - Migrants cross the Rio Grande into the U.S. from Mexico behind concertina wire and a sign warning that it's dangerous and illegal to cross, Jan. 3, 2024, in Eagle Pass, Texas.

January's decline in arrests for illegal crossings on the U.S. border with Mexico reflects how the numbers ebb and flow, and the reason usually goes beyond any single factor.