The porous nature of the border allowed most Mexican migrants to engage in circular migration. Most were men who would come to the United States, work here for a short period of time, return to Mexico to be with their families, and then repeat the process.

In 1986, however, the pattern of circular migration ended after Ronald Reagan signed into law the Immigration Reform and Control Act, or IRCA. Upon doing so, Reagan hailed: “Future generations of Americans will be thankful for our efforts to humanely regain control of our borders and thereby preserve the value of one of the most sacred possessions of our people: American citizenship.”

One of IRCA’s primary measures was to increase the enforcement budget of the Immigration and Naturalization Service. As a result, crossing the national boundary became a much more dangerous and expensive enterprise. To avoid detection, migrants had to pay smugglers to help them get across hazardous terrains that were less patrolled.

Despite the new hardships of migration, relatively few Mexicans reconsidered their decision to head north. On the contrary, the numbers of undocumented migrants continued to grow. While in 1986, an estimated 3.2 million unauthorized migrants lived in the United States, the number reached 5 million in 1996, and grew to approximately 11 million in 2006. Despite the increased fortification of the border, Mexicans continued going to the United States because of economic need. After all, the passage of IRCA did nothing to alter the low wages and high underemployment rates in Mexico. However, as sociologist Douglas Massey and others have shown, as crossing the border became increasingly hard after 1986, most migrants started refraining from going back and forth between the two countries and instead decided to settle permanently in the United States.

The increased fortification of the border after 1986 also altered the demographics of migration. Once men realized that they would settle in the United States, they encouraged their wives and children to head north with them. Women had traditionally refrained from migrating because they risked being sexually assaulted at the border. But their husbands now also faced much danger when they traveled to the United States. Instead of having men expose themselves to these hazards repeatedly, women started to risk the border once and head to the United States. The travel of women and children further contributed to the rise of undocumented migration in the years following 1986.

Only the Great Recession stopped and even reversed the growth of undocumented migration. After 2008, more Mexicans started returning to Mexico from the United States than those who crossed the border north. Some of them were unable to enter the United States because of the increased border enforcement in the mid-2000s that followed the terrorist attacks of September 11, 2001, while others had to leave because they were deported. But many others ceased to be interested in coming to or remaining in the United States. The slow recovery of the U.S. economy after 2008 and the decreasing number of jobs available to immigrants, particularly those in construction where many Mexicans worked, made the United States less attractive. Fewer migrants sought to risk their lives at the border to come and those who were already here but still had family members in Mexico returned home to be with them.