Global Data Storage Capacity Totals 295 Exabytes: USC Study

How much information is there in the world? University of Southern California researchers calculated that the world has access to enough data-storage capacity to hold 295 exabytes (295 followed by 20 zeros) of information.

There are reports aplenty about technology driving a data explosion. University of Southern California researchers actually sat down and calculated that humans can store, communicate and compute about 295 exabytes of information, or about 404 billion CDs.

In a study published Feb. 10 in Science Express, an electronic journal that provides select Science articles ahead of print, researchers examined data from more than 1,000 sources to calculate how much data-storage capacity exists. The study, which looked at data from 1986 to 2007, did not try to calculate exactly how much data actually existed.

"This is the first study to quantify humankind's ability to handle information and how it has changed in the last two decades," said lead author Martin Hilbert, a doctoral candidate at the USC Annenberg School for Communication and Journalism.

Hilbert and his team calculated the figure by first estimating the amount of data held on 60 analog and digital technologies during the period from 1986 to 2007. They considered everything from computer hard drives to obsolete floppy discs, and X-ray film to microchips on credit cards, he said.

"The world's technological information-processing capacities are growing at exponential rates," Hilbert said. General-purpose computing capacity is growing at about 58 percent per year, the study said. Telecommunications grew by 28 percent annually, and storage capacity grew by 23 percent, according to the study.

"Basically what you can do with information is transmit it through space, and we call that communication. You can transmit it through time; we call that storage. Or you can transform it, manipulate it, change the meaning of it and we call that computation," Hilbert said.

The calculated total, 295 exabytes refers to storage capacity in 2007, according to the researchers. This is about 80 times more information per person than was ever stored in the historic Library of Alexandria in Egypt, Hilbert told eWEEK. The actual number for 2011 is likely to be much higher.

Humans sent 1.9 zettabytes of information through broadcast technology such as televisions and GPS during that 21-year period, the study found. That's equivalent to every person in the world receiving 174 newspapers every day or every television in the world running for three hours a day, Hilbert said.

More than 65 exabytes of information was shared over two-communications technology, such as cell phones and e-mail. Communications have increased by an average of 28 percent every year since 1986. About 65 exabytes of information was shared in 2007, or the equivalent of every single person sending out the contents of six newspapers every day.

"Using word-based chat, one would need to chat for two months and three weeks nonstop to communicate the information that the average person telecommunicates through multimedia content in one day only," Hilbert said.

All this feels like unimaginable numbers. Just for comparison, an exabyte is equivalent to 1,000 petabytes, or a million terabytes. An exabyte has 20 zeros following the number. A zettabyte is 1,000 exabytes.

While performing calculations, the researcher discovered the digital age "began" in 2002, the first year there was more data stored on digital storage than on analog, Hilbert said. About 75 percent of stored information was in an analog format such as videocassettes and books in 2000. By 2007, the flip was nearly complete, with 94 percent of information stored in digital form, Hilbert said.

The various storage types examined read like a list of forgotten devices. In 1986, "vinyl long-play records" made up 14 percent of storage and audiocassettes made up 12 percent, according to the study. Digital storage first became a significant factor in 2000, when it accounted for 25 percent of total storage capacity. The proportion of paper-based storage such as books and newspapers declined, from a mere 0.33 percent in 1986 to 0.007 percent in 2007. However, that didn't mean information from paper sources declined, since in absolute terms, paper grew from 8.7 to 19.4 optimally compressed petabytes, the study estimated.

Priscila Lopez of the Open University of Catalonia co-authored the study with Hilbert. Hilbert said a copy of the Science article is available on his Website.