The number of U.S. adults who own an e-reader -- meaning devices like the Amazon Kindle and Sony Reader, not Apple's iPad -- has tripled over the last year, according to GfK MRI. Where 2.1 million adults owned an e-reader device in March-October 2009, that number has soared to 5.9 million in the same period of 2010.
What's more, the gender balance of e-reader ownership has evened out. Last year, 56% of e-reader owners were male, but that proportion has shrunk to 49% this year -- exactly matching the proportion of the total population. In a promising finding for marketers, e-reader owners also tend to be relatively affluent: 55% come from households with annual incomes over $100,000.
Turning to content, books were the most popular item consumed on e-readers, with 74.9% of GfK MRI respondents saying they had used the device to read a book in the past six months, compared to just 17.6% for newspapers and 15.3% for magazines.
Further gender disparities were seen in the types of content consumed, with men 43% more likely than women to have read a newspaper or magazine on their e-readers, and women 23% more likely to have read a book.
An earlier GfK MRI study of e-reader owners, conducted in the first half of 2010, found that they also showed a much greater propensity for using social network sites, especially those with professional relevance.
The GfK MRI survey found that e-reader owners were 64% more likely than the average U.S. adult to be a member of Facebook, 269% more likely to use Twitter, and a whopping 375% more likely to be a member of LinkedIn.
However, the number of e-reader owners has more than doubled since this earlier study; it's not clear whether the social network participation figures have changed as the number of e-reader owners increased.
In October, GfK MRI said it is preparing a full cross-platform measurement of magazine readership in 2011, covering all digital platforms, including Web sites, digital editions received via email, smartphone apps, e-readers and tablets, including Apple's iPad.