It is sometimes said that the hallmark of insanity is doing the same thing over and over again and expecting different results. This maxim succinctly describes the U.S. government’s long-standing approach to the problem of undocumented immigration. Since the mid-1980s, the federal government has tried repeatedly, without success, to stem the flow of undocumented immigrants to the United States with all sorts of immigration-enforcement initiatives: deploying more and more agents, fences, flood lights, aircraft, cameras, and sensors along the southwest border with Mexico — increasing the number of worksite raids and arrests conducted throughout the country — expanding detention facilities to accommodate the hundreds of thousands of undocumented immigrants apprehended each year — and creating new bureaucratic procedures to expedite the return of detained immigrants to their home countries.