According to its press release, Amazon.com is now selling more Kindle books than paperback books. Since the beginning of 2010, for every 100 paperback books Amazon has sold, the it has sold 115 Kindle books. Additionally, during this same time period it has sold three times as many Kindle books as hardcover books. The third-generation Kindle eclipsed “Harry Potter and the Deathly Hallows” as the bestselling product in Amazon’s history.
Other digital tipping points:
In 2008, more music was sold by iTunes than by Wal-Mart.
In 2003, for the first time, more digital cameras than traditional film cameras were sold in the U.S.
In June 2003, the DVD format (launched in the late 1990s) became more popular than VHS in the U.S.
In 1996, digital storage became more cost-effective for storing data than paper.
The Story of Information 