How big can this iPad thing get? A lot bigger still, apparently, based on new data from eMarketer (http://www.emarketer.com), a "digital intelligence" research firm. The company says 1-in-3 online consumers will use a tablet by 2014.

Tablet devices, in their current incarnation, have only been available for a couple years, but the iPad has propelled them to rapid increases in ownership and usage. eMarketer estimates that by the end of 2011, 33.7 million Americans will use a tablet device at least monthly -- a rise of 158.6% over last year, the year the iPad was released.

Growth will slow to double digits beginning in 2012. However, the number of users will rise to nearly 90 million, or 35.6% of all internet users, by 2014. eMarketer’s previous tablet-related forecasts have focused on unit sales and the total installed base of devices.

These current estimates deal instead with usage, and account for device sharing. eMarketer believes that as tablet adoption continues, less growth will come from sharing and more from replacing older devices with new ones. Eventually, tablets may become more like smartphones, which typically have a single user and less sharing.

The iPad, which has clearly led the tablet market since 2010, will continue to do so throughout the forecast period, though its share will be slowly chipped away by competititors. The number of US iPad users will more than double between this year and 2014, from 28 million to 60.8 million. By 2014 iPad users will still account for 68% of the overall US tablet audience.

The tablet audience is changing, though. Women currently account for slightly less than half of tablet users, but the disparity in tablet usage between sexes will continue to shrink. eMarketer estimates that this year, 31.5% of tablet users are ages 18 to 34, while 55.5% are 35 or older. By 2014, 18- to 34-year-olds will acount for 34.8% of tablet users, while those ages 35 and up will comprise 49.3% of the total. Usage of tablets wil also increase faster among whites than those of other races and ethnicities, growing from 60.6% of total users this year to 65.8% by 2014.

-- Dennis Sellers