An immigration reform bill in the Senate would create goals for border security over the next 10 years, and tie those goals to legalization of undocumented immigrants.
But we can't say whether the goals are feasible for a few reasons:
Under the Senate plan, the federal government would need to meet certain benchmarks before most undocumented immigrants would be able to seek legal status and citizenship.
It's a trade off: border security for legalization.
The first step toward legalization for most undocumented immigrants would be a provisional immigration status. But before anyone could apply for that status, the U.S. Department of Homeland Security (DHS) would need to submit a border security plan to Congress.
See Also: Is a More Humane Border Policy Possible?
The plan would spell out how the federal government would achieve 100 percent surveillance of the border and 90 percent effectiveness in catching people who are crossing illegally.
The tricky part will be gauging "effectiveness" in catching unauthorized crossers.
Right now, the most frequently cited measure for border enforcement is the number of apprehensions. But that only tells us how many people are caught. We also need to know how many people are crossing to have any idea if enforcement efforts are succeeding.
Border Patrol uses observational techniques to determine how many people have avoided detection, according to a government report drawing on data from the 2011 fiscal year.
That mostly means cameras, eyes and something called "sign cutting" -- tracking people by signs in the brush, like broken twigs or footprints. The AP reported that 83 percent of unauthorized crossers that the agency recorded as "getaways" during that period were determined through sign cutting.
But some researchers aren't sold on that approach.
A report released on Monday by the Council on Foreign Relations, a non-partisan think tank, found that the method used by Border Patrol produces a higher rate of success than other methods, like using survey data or rates of recidivism to create an estimate.
In the end, researchers need more government data to judge whether border operations are successful, according to Edward Alden, a senior fellow at the Council on Foreign Relations and one of the people who worked on the report.
But DHS has been reluctant to release information about how they count unauthorized crossers, and doesn't include the statistic in any kind of regular report. Border Patrol records other insightful stats, like the number of repeat crossers, but doesn't make that information publicly available.
"You need a decent measurement system for people coming in illegally," he said. "It's essential for reassuring people that progress is being made on this."
There's also some pretty ambiguous language in the Senate bill around border security.
As I mentioned, most undocumented immigrants won't be able to legalize until DHS has submitted a border security plan to Congress.
But there's another hurdle for those immigrants. After staying in their provisional status for 10 years, they'll be able to seek citizenship, but only if certain immigration enforcement promises have been fulfilled.
One of those promises is that the border security plan is "substantially deployed and substantially operational."
That doesn't mean that the country will have to fully achieve the goals in the plan (100 percent surveillance and 90 percent "effectiveness" in catching unauthorized crossers). It just means that the plan will need to be "substantially" up and running.
The vague language could be a worry for border hawks, who want to see increased enforcement. But it could also impact immigrants seeking legal status.
"I could see it being problematic in both instances," said Shiu-Ming Cheer, an immigration attorney with the National Immigration Law Center, a group that advocates for immigrant rights. "For people who are concerned about the trigger, they don't know if the process for people to become legal permanent residents is going to be held up."
Cheer believes that the federal government will need to define what it means by "substantially operational," either before or after the bill is passed. Otherwise, the term is subjective, and open to manipulation.