• by Mark Walsh  @markfwal, June 11, 2012

A new forecast from eMarketer predicts the number of U.S. tablet users will more than double this year from 33.7 million to nearly 70 million, or about 29% of the country’s Internet users. Responsible for most of that growth is the iPad, which remains the dominant tablet model, with more than three-quarters of the market in 2012.

The latest tablet findings were released Monday, as Apple launched the latest version of its iOS operating system for iPhones, iPads and iPod Touches.

The eMarketer report projects the number of iPad users will grow 90% this year to 53.2 million, down from 144% last year. That growth rate is expected to continue declining to 12% in 2015, when the number of iPad users will have reached 90.8 million. Likewise, the Apple tablet’s market share will gradually decline from a peak of 88% in 2010 to 68% in 2015 as competing devices gain some ground.

In terms of the total U.S. population, 16.8% are expected to use an iPad at least once per month this year, up from 8.9% in 2011. Among Internet users, that translates to 22.2% penetration, up from 12.1% last year. By 2015, more than a third (35.3%) of Internet users will have an iPad.

More than half (51.9%) of Internet users -- or 133.5 million Americans -- will have a tablet of some kind by then, eMarketer predicts. The 29% penetration the research firm projects this year would more than double last year’s 14.5% reach.

eMarketer estimates more than half of tablet users this year to be men (54%), but the gender split is expected to be roughly even in three years. With 26.2% penetration in 2012, Asians are the most likely racial or ethnic group to use a tablet, followed by Hispanics (24%), whites (21.4%) and blacks (21.5%).

Data released last month by IDC showed tablets shipments worldwide hit 17.4 million, up 120% from the year-earlier period, but 1.2 million shy of the technology research firm’s projection. Shipments of the Kindle Fire in particular fell sharply, dropping 62% from the prior quarter to 0.8 million units.

Apple’s relatively steady performance to start the year helped expand its share in the tablet market -- from a 54.7% share of shipments globally in the fourth quarter to 68% in the first quarter.