In his State of the Union Address, President Trump continued to insist on building a $25 billion wall along the Mexico-U.S. border—a farcical waste of taxpayer money. Undocumented migration from Mexico to the U.S. essentially ended ten years ago; the total number of Mexican immigrants has stabilized at around 11.7 million persons, as the number of undocumented Mexican migrants declines. This is to say, since 2008, the net number of Mexicans (in any legal status) entering the U.S. has been zero or negative.

The push for a border wall doubles-down on past failed policies and the particularly vulnerable population of women and children they created, yet no border wall can affect a migratory flow that has already gone negative.

Mexican migration to the United States was briefly curtailed during the depression years of the 1930s, but it began in the early 20^th century and was revived in 1942, when the U.S. government enacted a labor recruitment program to address wartime labor shortages. The program was expanded after the war, and, in the late 1950s, it sponsored the annual entry of around 450,000 temporary Mexican workers, accompanied by a yearly inflow of around 50,000 legal Mexican immigrants.  In 1965, Congress ended temporary worker entries and imposed new numerical limits on immigration from the Western Hemisphere.

The social and economic circumstances supporting migration on both sides of the border had not changed, however, and when opportunities for legal entry were curtailed, the flows simply reestablished themselves under undocumented auspices. Unauthorized migration rose after 1965 and peaked in 1979, with no sustained increases thereafter. During this time, undocumented migration was a circular affair dominated by male workers flowing to traditional destinations in a handful of states. In practical terms, nothing had really changed. However, the rise of “illegal” migration enabled the framing of Mexican migration as a grave threat to the nation, since the migrants were, by definition, “lawbreakers” and “criminals.”

The subsequent rise of a “Latino threat narrative” in the media hardened public attitudes toward immigration and led to a sustained increase in the personnel, materiel, and funding devoted to border enforcement.

From 1965 through 1985, undocumented migration remained overwhelmingly circular, with migrants earning money in the U.S. to finance investments and consumption in Mexico. The militarization of the border began with the Immigration Reform and Control Act of 1986, and it accelerated with the 1993 launch of Operation Blockade in El Paso and 1994 launch of Operation Gatekeeper in San Diego. It was again boosted by new restrictive legislation in 1996 and put on steroids with by the 2001 USA PATRIOT Act, which also increased internal deportations to unprecedented levels, putting intense pressure on undocumented migrants within the U.S.

The militarization of the border dramatically altered the character of Mexico-U.S. migration, deflecting flows away from traditional crossing points along the border with California and Texas and into the Sonoran desert through Arizona. The change dramatically increased the monetary costs and physical risks of unauthorized border crossing. Migrants responded not by staying home, but by remaining longer in the U.S. to avoid the aversive gauntlet at the border. As male workers stayed in the U.S., rates of return migration plummeted and family reunification ensued. Migrants arranged for the entry of their wives and young children (now popularly known as “dreamers”). And, as you might expect, with family reunification and longer stays came the births of U.S. citizen children. Now immigration enforcement efforts acquired a distinctly gendered dimension.

The escalation of deportations, first under Obama and then under Trump, has put great pressure on women trying to hold their families together.

Workplace raids have led to the widespread detention and deportation of male workers, which not only traumatizes their wives and children but leaves them in economically precarious circumstances. As time progresses, a growing number of U.S. citizen children are traumatized and impoverished in the name of border security.

Deportation raids are not confined to male-dominated workplaces, of course, and women themselves have inevitably been swept up in the enforcement dragnet and deported, creating an excruciating “Hobson’s choice” for mothers. Do they leave their U.S.-born children behind with relatives or friends so they can enjoy the benefits of American schooling and health care and grow up in their native culture? Should these mothers bring their children with them back to Mexico to live as undocumented foreigners?  Either option brings pain and suffering.

If the children remain in the U.S., they receive some material benefits, but bear the emotional costs of childhood without a mother.

We have no real way of knowing how many families have been ruptured in this fashion, but with annual deportations in the hundreds of thousands, it is clearly large. On the beach between Tijuana and San Diego, the border wall consists of a series of narrowly spaced metal shafts driven deep into the sand; mothers reach through the gaps with tears in their eyes to touch the hands of their U.S.-born children on the other side. It is a dramatic, daily enactment of the suffering caused by U.S. immigration actions.

On the other hand, deported mothers can bring their U.S. citizen children with them back to Mexico. From Mexican data sources, we know there are currently more than half a million such children living south of the border. Although these children benefit from uninterrupted access to a mother’s love, they are traumatized as they are uprooted from familiar surroundings and thrust into an alien culture. They may speak household Spanish, but most are unfamiliar with the formalities of the language and cannot read or write it very well. They know little about Mexican history and have only a superficial knowledge of Mexican popular culture. They are, after all, not Mexican children, but American ones.

Without Mexican citizenship and ID card, these children have trouble or are barred from accessing social services in Mexico.

And while the Mexican Education Ministry is making serious efforts to integrate these children into schools, the U.S. Embassy and its local Consulates are doing little to assist these vulnerable U.S. citizens. In local schools, the children are often bullied for not being “really Mexican,” with their halting Spanish and American ways. Their mothers are forced to witness the ongoing suffering of their children as they struggle to fit into a land they do not know.

U.S. policy militarized the border and transformed what had been a circular flow of male workers going to a few states into a large and growing settled population of families in all 50 states. Having created this vulnerable population, the U.S. has compounded its misery, unleashing a massive repressive policing effort upon its members. If that were not enough, President Trump seeks to build a $25 billion dollar wall to signal the nation’s contempt for those living south of the border. Again, a wall cannot affect a migratory flow that has already gone negative; thus its only real purpose is symbolic, a concrete demonstration that Latin Americans are not and never will be accepted as “real” Americans.