Global data storage calculated at 295 exabytes

By 2007, 94% of stored information was kept digitally

Mankind's capacity to store the colossal amount of information in the world has been measured by scientists.

The study, published in the journal Science, calculates the amount of data stored in the world by 2007 as 295 exabytes.
That is the equivalent of 1.2 billion average hard drives.
The researchers calculated the figure by estimating the amount of data held on 60 technologies from PCs and and DVDs to paper adverts and books.

"If we were to take all that information and store it in books, we could cover the entire area of the US or China in 13 layers of books," Dr Martin Hilbert of the University of Southern California.

Information revolution
Computer storage has traditionally been measured in kilobytes, then megabytes, and now usually gigabytes. After that comes terabytes, petabytes, then exabytes. One exabyte is a billion gigabytes.
The same information stored digitally on CDs would create a stack of discs that would reach beyond the moon, according to the researchers.
Scientists calculated the figure by estimating the amount of data held on 60 analogue and digital technologies during the period from 1986 to 2007. They considered everything from computer hard drives to obsolete floppy discs, and x-ray films to microchips on credit cards.
The survey covers a period known as the "information revolution" as human societies transition to a digital age. It shows that in 2000 75% of stored information was in an analogue format such as video cassettes, but that by 2007, 94% of it was digital.