How much phone data does NSA collect?

The National Security Agency collects less than 30 percent of U.S. phone records due to “technical challenges” involved with the influx of cellphone data, according to media reports.

The agency's phone data collection has dropped significantly since 2006 as it struggles to keep pace with consumers’ shift away from landlines.

It has faced issues in customizing its system to handle the increase of cell data while not sweeping in cell tower and location-based information, which the agency is not legally authorized to obtain. The records include numbers called and call duration.

Eight years ago, the NSA was collecting “almost 100” percent of bulk call data, an anonymous senior U.S. official told the Washington Post Saturday. 

While officials told the Post that collection stands at under 30 percent, the Wall Street Journal pegs the telephone metadata collection levels at fewer than 20 percent – spurring questions about the legitimacy of the program. 

"The one question that has not been adequately answered is whether this program is effective," Nancy Libin, a former chief privacy officer at the Justice Department under President Obama, told the Journal. "You don't want to intrude on people's privacy and undermine public trust if it's not going to do any good." 

The program began under George W. Bush, but gained newfound notoriety last year when former NSA contractor Edward Snowden leaked details about the government’s vast surveillance. 

NSA officials have defended the program, saying having all the communications data available is necessary to maintaining national security, because it enables them to have a complete picture of terrorist activities.

“I believe it is in the nation's best interest to put all the phone records into a lockbox that we could search when the nation needs to do it,” NSA Director Keith Alexander told a Senate panel last year.

While Obama initially stood by the NSA’s various types of surveillance programs last June, saying, “at least 50 attacks have been averted because of this information,” he has since changed his stance.

In December, a White House panel investigated the domestic telephone metadata collection and concluded that it is “not essential in preventing attacks.” 

“There has been no instance in which NSA could say with confidence that the outcome [of a terror investigation] would have been any different” without the program, the panel’s report found.

The revelations have spurred calls for reform from government officials, watchdogs and civil rights groups.

Last month, Obama announced plans to take the telephone data out of government control, shifting the mass information to a third part or private company – and gave Justice Department and intelligence officials until March 28 to come up with a plan.