ComScore, a leader in assessing the digital world, has released its monthly comScore Search analysis of the U.S. search marketplace.

The report said that Americans conducted 13.5 billion searches at the core search engines during the last month (Jan 2009), a 7 percent increase as compared to December 2008.

According to report, Google Sites handled 8.5 billion core searches, followed by Yahoo! Sites with 2.8 billion and Microsoft Sites with 1.1 billion.

The report also said that Google Sites topped the U.S. core search market during December with 63% of the searches conducted, accompanied by Yahoo! Sites with 21%, Microsoft Sites with 8.5%, AOL LLC with 3.9% and Ask Network with 3.7%.

In the comScore January 2009 analysis of the top properties where search activity is observed, Google Sites continued to gain the top position with 11.7 billion searches, up 5% as compared to December 2008.

On the other hand, Yahoo! Sites ranked second with approximately 3 billion searches, followed by Microsoft Sites (1.2 billion) and AOL LLC (781 million).