The National Security Agency's program to mine electronic data from America's biggest internet companies is mind-boggling in scope. The top-secret effort — code-named PRISM — is reportedly aimed at cross-checking emails and other information exchanged by foreign targets to head off potential threats against the U.S. (Read our helpful primer on PRISM here.) Just how much of an intelligence goldmine is PRISM to analysts trying to foil terrorist plots, and how deeply did they delve into Americans' private information? Here, a look at PRISM's reach, by the numbers:

Internet companies whose servers the NSA allegedly tapped, according to documents leaked to The Washington Post and The Guardian. The tech giants affected are reportedly Microsoft, Yahoo, Google, Facebook, PalTalk, YouTube, Skype, AOL, and Apple.

Companies on the list whose executives say they never knowingly gave the NSA access to their servers

Times that Twitter information has been involved in PRISM

Percentage of PRISM data that has been collected from Google, Yahoo, and Microsoft (which is currently running an ad campaign under the slogan "Your privacy is our priority")

Percent confidence PRISM searches are supposed to have of the targeted user's "foreignness," to prevent snooping on American citizens abroad or anyone inside the U.S.

Section of the Foreign Intelligence Surveillance Act that James Clapper, the director of National Intelligence, says makes PRISM "entirely legal"

Years the PRISM program was in operation before The Washington Post and The Guardian got their hands on a PowerPoint training presentation that was apparently leaked by a career intelligence officer concerned that PRISM is a gargantuan violation of privacy

PowerPoint slides on PRISM included in the presentation leaked to The Washington Post

Intelligence reports that have cited PRISM

Times PRISM data was cited in the President's Daily Brief last year, making it the most prolific source of intelligence information for President Obama's regular national security updates

1 in 7
Intelligence reports generated by the NSA that rely on data from PRISM, which the Post says makes the program the NSA's leading source of raw material

Reports based on PRISM in 2012 alone, suggesting significant growth in the use of the program. Intelligence officials say the program has helped them keep up with an exponential increase in communication among terrorism suspects using social media.

Percent growth in PRISM requests for Skype data in 2012

Percent increase in requests for Facebook information in the same year

Percent increase in requests for Google information in 2012

$20 million
Annual cost of the program

Sources: Foreign Policy, Guardian, The Next Web, TIME, Washington Post