(CNN) -- During Tuesday night's State of the Union address, President Barack Obama touted his administration's efforts on reducing illegal immigration.
"Real reform means stronger border security, and we can build on the progress my administration has already made -- putting more boots on the southern border than at any time in our history, and reducing illegal crossings to their lowest levels in 40 years."
That's a big claim, so CNN decided to take a closer look.
In fiscal year 2011, there were 18,506 U.S. Border Patrol agents in the Southwest Border Sectors -- up steadily from 3,555 agents in 1992, according to Customs and Border Protection figures.
A Pew Research Hispanic Center study finds that Border Patrol apprehensions of all unauthorized immigrants are at their lowest level since 1971. "In spite of (and perhaps because of) increases in the number of U.S. Border Patrol agents, apprehensions of Mexicans trying to cross the border illegally have plummeted in recent years—from more than 1 million in 2005 to 286,000 in 2011—a likely indication that fewer unauthorized migrants are trying to cross," it concluded.
Pew estimates that net migration -- newly arrived immigrants minus those leaving (forced or voluntarily) -- has come to a standstill, which it attributes to the weakened U.S. job and construction markets, border enforcement, an increase in deportations, and increased dangers associated with crossing the border.
In all, there were 327,577 illegal immigrant apprehensions in 2011, according to the U.S. Border Patrol. This is the lowest number since 1972, when there were 321,326. According to the Department of Homeland Security, the 2011 figure is a 53% drop from 2008, which it says indicates that fewer people are trying to cross the border.
The figures can be tough to interpret. Often, the same person is caught more than once, "and then the flip side of that phenomenon is there's no way of knowing how many you missed counting, how many do get through," said Dan Kowalski, editor of Bender's Immigration Bulletin and an immigration lawyer at the Fowler Law Firm in Austin, Texas. "So, you get what you measure. In other words, you count what you count."
But even if the border could be sealed in a foolproof manner, the issue of illegal immigration would not be resolved. That's because many of those people who are in the United States without authorization have entered the country legally on a visa and simply overstayed their visa status, Kowalski said.
Obama's comments appear to accurately summarize the current state of illegal immigration, though it's impossible to determine with certainty how many illegal crossings may have occurred.