Google might still be the leading search engine in the U.S. by a large margin, but over the last six months, searches powered by MicrosoftBing are increasing at an impressive rate. So impressive, in fact, that if the trend line continues, there will be a real contest between Bing and Google next year — and Bing may just come out on top.

Research shows Google was responsible for 64.42% of searches in the U.S. in March, 2011. Bing-powered search — which includes both search.yahoo.com and bing.com — accounted for 30% of U.S. searches.

Bing vs Google

The scenario: if Google drops 3% of its market share each month, while Bing gains 5% each month. Of course, this assumes sustained growth and sustained losses on the parts of both search engines. In a volatile market, it is extremely unlikely that we’ll see these exact numbers over the next year.

But if you do assume a constant trajectory, Bing will overtake Google in less than a year — January 2012, to be precise.

At the moment Bing has real momentum and after years of referring to Google as “the search giant”, it looks as if there is a serious contender for that title — and we could be heading towards an era dominated by two search superpowers.