There are very few innovations where the point that critical mass was achieved can be pinpointed as clearly as it can for eBooks. Critical mass refers to the point where there are sufficient devices to encourage production of content, and their is sufficient content available to encourage acquiring the eReader devices to access the content. For eBooks, last fall saw a significant expansion in the range and variety of eReaders available, along with the reduction in costs and prices to open up demand. Sales of eReaders boomed during the Christmas season, and has continued to grow. One report had global eReader sales in the last quarter of 2010 topping 5 million, almost double that of the previous quarter. A new report from the Pew Internet & American Life Project found ownership of eReaders in the U.S. grew from 6% in November 2010, to 12% in May 2011. Between the growth in eReader availability and Amazon's leadership in offering free eReader apps for a range of computers, smartphones, and tablets, critical mass in display devices was clearly reached at some point during last Fall's Christmas season.
Critical mass for content was also likely reached around the last quarter of 2010, with Amazon doubling the number of eBook titles offered (with over 800,000 titles available in December, 2010, and the entry of other large eBook stores (Apple's iBook (selling 100 million books in its first year), and Barnes & Noble). The final indicator of critical mass is the explosion in eBook sales. As of last February, eBook sales in the US had tripled from the previous year, becoming the number one format among those recognized by the Association of American Publishers. The value of eBook sales in the US was being forecast to grow from around $300 million in 2009 to $2.7 billion in 2013. eBook sales are on a pace to surpass $1 billion this year.
So it looks like eBooks will be quite a successful innovation, expanding and competing with the traditional book markets. Other recent research suggests that eBooks aren't displacing print books as much as supplementing and expanding traditional book markets.
Updated: To fix formatting issue with second graphic
Sources: "e-Reader ownership doubles in six months." Pew Internet & American Life report.
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