Source: Asymco

By the fourth quarter of 2012, there will be 1 million new smartphone users in the United States each week, according to analysts over at Asymco. The analyst group has been tracking monthly metrics offered up by comScore for the past two years, which yielded the surprising prediction. January saw a still very impressive 767,000 new smartphone users each week on average, down from the 1.5 million weekly adds in December but up from the unusually low numbers for November (less than 500,000 each week).

Asymco also noted that "a significant 35 million" US consumers switched to smartphone during the past 12 months. According to the firm, about 43 percent of people 13-years-old and older now have smartphones for personal use. That percentage does not include business purchases (oddly). The firm predicts that 50 percent of people in the US will have smartphones by the end of June 2012.

Google's Android now counts about 50 million smartphone users in the US, while the iPhone has about 30 million users. There are now about half as many BlackBerry users (15 million) as iPhone users, according to the firm. Those using smartphones running some kind of Windows number less than 5 million.

The dominant platforms, Android and iPhone, are continuing to make gains while their rival's user bases shrink, according to the firm.

Here's how Asymco sums it up: "The two trends that continue are that overall penetration is nearing saturation and that two platforms seem to be increasing their share of that base. The 'comeback story' for any of the hopefuls will depend either on switching users away from their current platforms of trying to engage with late adopters. The first option is daunting due to latent network effects related to platforms and the second sounds to be symmetric to existing incumbent strategies."

Many more interesting charts and figures in this Asymco post.