Dive summary:

• Yahoo's share of the search market dropped from 12.8% to 12.2% from August to September.
• The company had 15.5% of search engine users in September 2011.
• Bing saw the biggest gain in search engine users during the past year from 14.7% to 15.9% since September 2011.

From the article:

The figures above don’t reflect mobile search, which represents a growing share of overall query volume. Indeed, earlier today digital agency RKG released a report that asserted non-PC devices (smartphones and tablets) combined to drive 21 percent of overall organic search traffic in Q3. ...