An auto worker tightens bolts on a Focus at a Ford plant in Michigan in October. Labor unions predicted in 1993 that NAFTA would send many U.S. manufacturing jobs to Mexico, and they continue to argue that the pact prompted a race to the bottom for workers. Mira Oberman/AFP/Getty Images hide caption

itoggle caption Mira Oberman/AFP/Getty Images

Freshly caught catfish wriggle in large nets in Doddsville, Miss. Jackie Northam/NPR hide caption

itoggle caption Jackie Northam/NPR

A truck bearing Mexican and U.S. flags approaches the border crossing into the U.S., in Laredo, Texas. Reuters /Landov hide caption

itoggle caption Reuters /Landov

Kayakers head out on the Rio Grande toward one of the international bridges that connect Laredo, Texas, and the town of Nuevo Laredo in Mexico. Raw sewage and animal carcasses float in the water. Neena Satija/Texas Tribune hide caption

itoggle caption Neena Satija/Texas Tribune