Trump wants a seamless wall on the U.S. southern border to stop migrants mostly from Latin America. Orban wants to fence off the European Union to keep out refugees from Syria, Afghanistan, and troubled countries in Africa. Orban’s government has completed a 100-mile-plus razor wire fence along its border with Serbia, now extending into Croatia and Romania.

Both Trump and Orban whip up public fear and then offer themselves as the protectors of their nations in return for votes. But building higher walls and digging deeper moats solves few problems while incurring serious human and financial costs.

Ironically, fences seal in unauthorized immigrants once they manage to enter the country. In the U.S. case, a serious border buildup began in the mid-1990s. Academic research and independent assessments by the U.S. Government Accountability Office show that increased enforcement made unauthorized immigrants stay in the United States for longer periods — to avoid the physical risks and high costs of repeatedly going back and forth in clandestine crossings. For at least the first 15 years, the federal government’s own data reveal a dramatic increase in the number of unauthorized Mexicans living in the United States .