Americans conducted 15.9 billion searches in the month of May – up 3 percent from April, reports comScore. It is likely unsurprising that Google led the pack, but it may be of interest that Yahoo and Bing are taking a new search approach that is leading comScore – and perhaps ultimately marketers – to change search engine evaluation methods.

The study reveals that Google accounted for 10.2 billion U.S. searches – up 2 percent from last month. Yahoo and Bing still lag far behind, however each search engine garnered 6 percent more searches over April. Yahoo accounted for 2.9 billion searches (18.3 percent overall) and 1.9 billion searchers used Bing (12.1 percent overall).

The large gains demonstrated by the two search engines are perhaps linked to Yahoo and Microsoft’s use of contextual search approaches. In a comScore blog, Cameron Meierhoefer explains this approach makes relevant search result pages part of the results presented to queries, linking users to other Bing or Yahoo search pages.

Skeptics say this tactic inflates the search engines‘ overall rankings, but comScore officials believe this strategy provides consumers with intuitive and convenient content to refine their own searches, while simultaneously leveraging use of the host search engines‘ services.

Moreover, Meierhoefer explains that "context driven searches are sometimes monetized at different rates." As BizReport says, paid searches account for about $29 billion in ad revenues. Marketers may want to investigate contextual result ad rates as they plan their campaigns for Bing and Yahoo.