Americans carried out 13.5 billion searches in the month of January 2009. This figure is 7% higher than the corresponding figure just one month ago, in December 2008.

Expectedly, Google sites were the leaders in the number of searches conducted with 59% share of the market, followed by Yahoo! sites having 15% market share and Microsoft sites having 6% share of the market. AOL and the Ask Network had 3.9% and 3.7% respectively.

Of the 11.7 billion (up 5% from December 2008) searches conducted across all Google sites in January 2009, Google Search accounted for 75% while YouTube and other Google sites contributed to 25% of the volume.

Yahoo! and Microsoft’s search metrics are much more heavily skewed towards their main search properties, with both contributing to 99% of their individual total volumes.

AOL and the Ask Network, on the other hand, had a much more even distribution. 58% of AOL searches coming from the search network while 42% came from MapQuest and other AOL properties. Less than half (49%) of the Ask Network’s searches came from Ask.com while 51% came from MyWebSearch and other properties.

A comparison with the same period a year ago shows that Google’s market share grew 6% points between January 2008 and January 2009, while that of Yahoo! fell 2% points and Microsoft fell 1% point.

Yahoo!, though, has actually gained market share for the fifth consecutive month now, at the expense of Microsoft and Ask.com mostly, but also at the expense of Google last month.

The graph alongside holds few surprises. Google has consistently held its pole position in the ranking of search engines. In January 2008 alone the search giant received 7.7 billion search requests on its combined properties, which include Google Search (6.2 billion searches) and YouTube (1.5 billion).

Google’s market share in the US crossed 50% in September 2007, and it hasn’t fallen below the half way mark since then. Yahoo! continues to trail far behind with 2.5 billion searches, followed not as far behind by Microsoft with 1 billion searches. If the 2nd and 3rd ranking players in the market were to join forces, their combined search volumes would be 3.5 billion, accounting for 24% market share.

Over the past 6 months Google has continued to grow at the expense of its competitors. The graph below compares the growth in number of search queries received on each of the Top 5 ranked search engines.

Google grew 14% in terms of the number of queries received over the past six months. Even though all the providers grew in Jan 2008 compared to December 2007, the six-month numbers are not as good for anyone other than Google. Both Yahoo! and Microsoft have fallen, the latter by as much as 7% compared to August 2007 numbers.