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Exabytes, zettabytes

Someone has added up all the data that we've created. The cold, hard truth: It's too much to store.

A new study that estimates how much digital information the world is generating (hint: a lot) finds that for the first time, there's not enough storage space to hold it all. Good thing we delete some stuff.

The report, assembled by the technology research firm IDC, sought to account for all the ones and zeros that make up photos, videos, e-mails, Web pages, instant messages, phone calls and other digital content zipping around. The researchers assumed that on average, each digital file gets replicated three times.

Add it all up and IDC determined that the world generated 161-billion gigabytes - 161 exabytes - of digital information last year.

Oh, the equivalents! That's like 12 stacks of books that each reach from the Earth to the sun. Or you might think of it as 3-million times the information in all the books ever written, according to IDC. You'd need more than 2-billion of the most capacious iPods on the market to get 161 exabytes.

The previous best estimate came from researchers at the University of California, Berkeley, who totaled the globe's information production at 5 exabytes in 2003.

But that report followed a different trail. It included nonelectronic information, such as analog radio broadcasts or printed office memos, and tallied how much space that would consume if digitized. And it counted original data only, not all the times things got copied.

In comparison, the IDC numbers were made much higher by including content as it was created and as it was reproduced - for example, as a digital TV file was made and every time it landed on a screen. If IDC tracked original data only, its result would have been 40 exabytes.

Still, even the 2003 figure of 5 exabytes is enormous - it was said at the time to be 37,000 Libraries of Congress - so why does it matter how much more enormous the number is now?

For one thing, said IDC analyst John Gantz, it's important to understand the effects of the factors behind the information explosion - such as the profusion of surveillance cameras and regulatory rules for corporate data retention.

The supply of data technically outstrips the supply of places to put it.

IDC estimates that the world had 185 exabytes of storage available last year and will have 601 exabytes in 2010. But the amount of stuff generated is expected to jump from 161 exabytes last year to 988 exabytes (closing in on 1 zettabyte) in 2010.

"If you had a run on the bank, you'd be in trouble," Gantz said. "If everybody stored every digital bit, there wouldn't be enough room."