WASHINGTON – As GOP senators prepare to fortify the border between the United States and Mexico, figures from the Customs and Border Protection show that the number of apprehensions and removals have decreased at the same time the number of agents has increased.

The Senate bill, which is scheduled for a full vote this week, includes the Corker Amendment, a $30 billion proposal to increase border security with a 700-mile-long fence along the Southwest border and an increase in 20,000 border agents.

The bill has the apparent support of both Colorado senators.

Although flight delays kept Sen. Mark Udall from voting Monday night on a motion to keep moving forward with immigration legislation, the Senate still voted 67-27 to push it toward final passage.

As the numbers show, apprehensions and removals took a sharp decline in 2000 and another dip in 2006. A spokesperson at the Department of Homeland Security said the increase in resources at the Southwest border deterred border crossings and apprehensions since 2006.

Apprehensions may have decreased because the number of Mexicans attempting to cross the border plummeted during the last decade, according to Pew data. Following a weakened U.S. economy in 2008, Mexican migration to the U.S. started to slow. At the same time, Mexico’s economy has taken a turn for the better, with a burgeoning middle class and growing economic opportunities.

“You have to be more nuanced when you look at the border,” said Duncan Wood, director of the Mexico Institute at the Woodrow Wilson Center, a think tank in Washington.

Wood said there is more than one reason for the decline in apprehensions, including the increased number of border agents that may have deterred more immigrants from entering. Anti-immigrant sentiment in states such as Arizona also played a key role in the decline of Mexican immigration. Still, Wood said that while border agents and technology have increased – particularly in urban areas of the border – immigrants continue to slip through other porous parts.

“As the border becomes harder, all those things have served as a deterrent, but migrants have been directed to other parts of the border,” he said. “Migrants are moving to more-dangerous parts of the border in the wilderness, and that’s the human cost.”

The cost of crossing the border comes at a deadly price, said Michael Danielson, a doctoral candidate at American University focusing on migration.

“The border is increasingly dangerous and controlled by criminal organizations,” Danielson said. “People are getting extorted by hired migration guides, and that increasing danger makes people less eager to go.”

Danielson prepared a report for the Kino Border Initiative, a Jesuit organization that aids immigrants on the border at Nogales, Ariz. His report found 430 immigrants who were verbally abused by border agents.

Adam Bozzi, spokesman for Sen. Michael Bennet, D-Colo., said the new bill will include a provision for a border oversight task force.

“The bill says (Homeland Security) has to develop and implement policies regarding use of force by its agents and a complaint-and-review process related to its use of force,” Bozzi said.

In a statement, Customs and Border Protection, a branch of Homeland Security, said it “stresses honor and integrity in every aspect of our mission.”

“The overwhelming majority of CBP employees and officers perform their duties with honor and distinction, working tirelessly every day to keep our country safe. We do not tolerate corruption or abuse within our ranks, and we fully cooperate with any criminal or administrative investigations of alleged misconduct by any of our personnel, on or off duty.”

Leigh Giangreco, a recent graduate of American University in Washington, D.C., is working as an intern for The Durango Herald.