Story by

Tia Ghose

A little randomness in deploying Border Patrol agents might work best to prevent illegal border crossings, according to a study from the RAND Corp.

The study, which was funded by the Department of Homeland Security's Science and Technology Directorate, found that combining historical data on illegal crossings with a bit of unpredictability would nab the highest fraction of border crossers.

The U.S.-Mexico border spans nearly 2,000 miles. Given its vastness and varied terrain, there is simply no way to saturate every mile with enough agents to catch every illegal immigrant or smuggler, said Joel Predd, study co-author and a researcher at RAND. The Border Patrol therefore must develop effective strategies to deploy a limited number of agents, he said.

In the past, the Border Patrol stationed agents by relying heavily on historical trends of where border crossers were apprehended, said Randy Capps, a senior policy analyst at the Migration Policy Institute, a think tank that studies worldwide migration patterns.

"As it has been, it's pretty predictable where resources are going to be deployed. They announce an operation, they do an operation, and they stay there a long time." 

The trouble with that strategy is that once crossers notice increased enforcement, they might alter their routes and actually have a higher rate of success in unpatrolled areas.

For instance, after the Border Patrol launched Operation Gatekeeper in 1994 to halt the flow of traffic through San Diego, illegal entries there plunged, but overall apprehensions continued to climb. In general, rising apprehension numbers could mean better enforcement, higher overall traffic or some combination, Predd said. 

The RAND researchers conducted field interviews with agents to learn about illegal crossing trends, staffing levels, patrol strategies and past deployment patterns. They created simulations of individual Border Patrol agents and crossers and modified where agents were placed using past patterns in illegal crossing, random distributions or a combination of both. They also drew from real data to create comparisons and metrics for different stations across the border. 

A mix of strategies worked best to catch the highest fraction of crossers.

"We looked at thousands of scenarios based on the number of zones, number of patrol agents, the daily rate of illegal smuggling," Predd said. "The idea that you should combine the two and shouldn't really use them in isolation is really robust across a wide range of values."

The study had a few limitations. For instance, it didn't address the geographic conditions that constrain crossers' ability to shift their routes, Predd said. Some remote, mountainous regions of the border are almost impossible to cross, while others are close to urban centers and transportation routes. Weather and seasonal conditions also might prevent crossers from changing their routes.

The Border Patrol claims that increased and more effective border enforcement already has caused the number of illegal crossings to plummet. The agency nearly doubled [PDF] the number of agents from 2005 to 2011 and has built hundreds of miles of fencing and sensors.

In the same time span, the number of illegal immigrants apprehended [PDF] dropped from 1,189,075 people to 340,252, with most of the decline occurring in the years after the recession started in 2007.  

While beefed-up enforcement might have deterred some would-be crossers, Capps said other factors may have more impact on border-crossing trends. The U.S. economy has floundered since the recession, while the Mexican economy has done relatively well, reducing the incentive to make the arduous journey, he said.

Demographics also might play a role.

"The birth rate has been low there for a number of years," Capps said. "This large pool of people who could potentially migrate to the U.S. from Mexico is just much smaller than it was even five to 10 years ago, and it's going to continue to decline."

"You have less incentive, more opportunities at home, and it's harder," he said.