Digital data now come in exabytes

Megabytes are dead.

Gigabytes are passe.

So much digital data now moves around the globe that those whoendeavor to measure it employ a new - or new to non-nerds - term.

Meet the exabyte.

How much data is an exabyte? It's a billion gigabytes - and itsignifies just how digital and data-intensive the world has become.

In 2007, the global capacity to store digital information - oncomputer hard disks, smartphones, CDs and other digital media -totaled 276 exabytes, a new report finds.

How much is that? Imagine a stack of CDs - each holding analbum's worth of digital music - shooting from the top of your deskto 50,000 miles beyond the moon.

But not everyone has equal access to those resources. In fact,the digital gap between rich and poor countries appears to begrowing, said Martin Hilbert of the University of SouthernCalifornia, who led the audacious effort to tally all ofcivilization's information and computing power.

In 2002, people in developed countries had access to eight timesthe bandwidth - or information-carrying capacity - of people inpoorer nations, Hilbert said, citing data he will publish soon. By2007, that gap had almost doubled.

"If we want to understand the vast social changes underway in theworld, we have to understand how much information people arehandling," Hilbert said.

To address that question, Hilbert and co-author Priscila Lopezspent four years poring over 1,110 sources of information spanningfrom 1986 to 2007, including sales data from computer and cellphonemakers and the music and movie industries.

In 1986, a year after digital CDs widely debuted, vinyl recordsstill accounted for 14 percent of all data on Earth, withaudiocassettes holding an additional 12 percent.

By 2000, digital media accounted for just 25 percent of allinformation in the world.

After that, the prevalence of digital media began to skyrocket.In 2002, digital storage capacity outstripped the non-digitalvariety - mostly paper and videotapes - for the first time.

"That was the turning point," said Hilbert, who published thereport in the journal Science. "You could say the digital agestarted in 2002. It continued tremendously from there."

By 2007, the last year documented in the study, 94 percent of allinformation storage capacity on Earth was digital. The other 6percent resided in books, magazines and other non-digital formats,particularly videotape, Hilbert and Lopez found.

But despite the forecasts of futurists, a paperless world has notarrived. Although stupendously outstripped in growth by digitalmedia, the amount of paper produced for books, magazines, newspapersand office use climbed steadily over the two decades of the study.

As for computing power - the number of calculations per secondavailable in all of the computers in the world - that grew fasterthan even information storage, muscling ahead at an average annualgrowth rate of 58 percent over 21 years. Information storage, incontrast, grew at a rate of 23 percent.

Of course, for anyone tethered to an iPhone, Gmail and Facebookall day, all of this probably comes as no surprise.

That daily digital activity contributes to a churning informationtsunami. Humans generate enough data - from TV and radio broadcasts,telephone conversations and, of course, Internet traffic - to fillour 276 exabyte storage capacity every eight weeks, Hilbert said. Ofcourse, most of the digital traffic is never stored long term,evaporating into the ether.

The study prompts deep questions, one of which Hilbert plans toexplore soon: How much of this data deluge is truly useful? Or, asHilbert distilled it, "What's the value of watching a silly catvideo versus reading an overpriced book?"

While we wait for an answer, social scientists worry that themounting data carry a hidden cost: disconnection from one another.

"We'd like to think that [information technology] changeseverything, that the amazing statistics these authors cite mean thatour society has fundamentally and irreversibly changed," said ThomasJ. Misa, who studies the history of technology at the University ofMinnesota. "I'm a bit more skeptical." After all, Misa said, "thereare still secret prisons in Cairo where government agents savagelybeat people. Cellphones and social media didn't change that."

Perhaps not, but widespread reports from Egypt suggest thatonline social networking contributed to - or even prompted - theongoing demonstrations there.

The study also found that Earth had 3.4 billion cellphones in2007, with telecommunications traffic growing at an average rate of28 percent per year between 1986 and 2007. That's a lot of minuteson your plan.

In a second report Hilbert plans to publish in a few months, hefound that an ever-increasing slice of our daily data resides not onhome computers and the smartphones in our pockets, but in giant datawarehouses owned by Google, Facebook, Citibank, the federalgovernment and other huge entities. Microsoft's recent ad campaigntouts the benefits of moving all of your personal data to "thecloud," invoking white puffs that magically - and cleanly - storeour home photos.

The reality is much dirtier. In 2006, the nation's "server farms"- the home of the cloud - sucked down 1.5 percent of all electricityin the United States, double the amount used in 2000, theEnvironmental Protection Agency reported. Congress ordered thereport out of concern that our insatiable demand for Facebook andYouTube would push the United States to build 10 new pollution-spewing coal plants.

But Hilbert offers a humbling comparison. Despite our gargantuandigital growth, the DNA in a single human body still stores far moreinformation - and a single human brain computes far morecalculations - than all the technology on Earth.

"Compared to Mother Nature," Hilbert said, "we are humbleapprentices."

vastagb@washpost.com