Jumptap just released its January 2012 mobile metrics report. There are a number of interesting things in the document. Among them, Jumptap saw a meaningful decline in iOS share of traffic over the course of 2011. This is consistent with what others have reported.

In general Android now has a little less than twice the market share of the iPhone in the US. However, December data show an surge in iPhone growth because of the 4S. 

ComScore released the following market share data for smartphones in Q4. Android grew 2.5%, which was nearly matched by the iPhone on a percentage basis.

Here's previously released Nielsen data regarding smartphone share among recent US buyers. 

Another very interesting datapoint from Jumptap is the relative CTR rates of ads on Android and iOS devices. According to Jumptap, with successive versions of the OS, CTRs have gone in opposite directions for iOS and Android. Jumptap had no good explanation for the trend. 

Jumptap also presented a chart showing the relative usage of apps and the mobile web. In December they saw roughly equal shares of usage: 

• Apps: 50.7%
• Mobile Web: 49.3%

Compare comScore apps vs. mobile web share for December, 2011 (comparable in share):

• Apps: 47.6.%
• Mobile Web: 47.5%

Finally Jumptap offered some tablet traffic comparisons on its network as of December 31, 2011:

• iPad: 44%
• Kindle Fire: 30%
• Other: 26%

What this would suggest is that non-iPad tablets have a majority share of traffic (56% to 44%) in the US. This probably calls into question whether Jumptap's network is representative of the US mobile market as a whole.