Gerry McGovern provides some very interesting statistics in a (fairly recent) book, Content Critical:

– Every issue of the New York Times contains more information that a 17th century individual would have read in a lifetime.
– There is enough scientific information written every year to keep a person busy reading day and night for 460 years
– In the last 30 years we have produced more information than in the previous 5,000
– The amount of recorded scientific knowledge is doubling approximately every fifteen to twenty years
– Over 1,000 books are published around the world every day
– Every day there are 7 million new documents published on the Web, where there are already over 550 billion.
– The world produces between one and two exabytes of unique content per year, which is roughly 250 megabytes for every man, woman, and child on earth.