BOSTON, USA: Bing's monthly market share in the US and globally has fallen for the first time since its launch, according to analysis conducted by web analytics firm StatCounter.

The firm's research arm StatCounter Global Stats finds that Bing's share of the US search market in September fell by over one percentage point to 8.51 percent from 9.64 percent in August.

There was little consolation for Microsoft from the performance of its new partner, Yahoo! which also declined, to 9.40 percent from 10.50 percent.

"The trend has been downwards for Bing since mid August," commented Aodhan Cullen, CEO, StatCounter. "The wheels haven't fallen off but the underlying trend must be a little worrying for Microsoft."

Google was the beneficiary from the decline of its main rival, increasing by more than two percentage points to 80.08 percent in September from 77.83 percent the previous month.

Globally, Bing also declined slightly to 3.25 percent from 3.58 percent, a trend mirrored by Yahoo! which fell to 4.37 percent from 4.84 percent. Google breached the 90 percent mark to 90.54 percent, similar to its global market share a year previously (90.53 percent).

Data is based on an analysis of 4.6 billion search engine referring clicks (1.1 billion from the US) which were collected during the period September 2008 to September 2009 from the StatCounter network of over three million websites.

StatCounter, which provides free website traffic analysis, is one of the largest web analytics firms in the world monitoring in excess of ten billion pageloads per month.