Bing is making progress in certain search verticals, says new data from Experian Hitwise, even as its overall slice of the U.S. search market remained roughly the same in March.

According to Experian Hitwise's April 7 research note, Bing's U.S. market share dipped from 9.70 to 9.62 percent between February and March. That 1 percent loss was mirrored by Google, which fell from 70.95 to 69.97 percent during the same period. Perhaps surprisingly, search.yahoo.com posted a 3 percent gain, from 14.57 to 15.04 percent of total searches. Ask.com enjoyed a 21 percent rise, from 2.84 to 3.44 percent market share.

Once you drill down a little more, what's particularly interesting is Bing's growth in verticals. Between March 2009 and March 2010, according to Hitwise, the search engine saw its share of traffic for Automobile searches expand by 102 percent, Health searches by 125 percent, Shopping by 106 percent and Travel by 85 percent. By contrast, Google experienced year-over-year gains of up to 12 percent (for Shopping) in those verticals, although its total market share in all areas continues to outpace Bing by double digits. The data is based on monthly upstream traffic from Hitwise's sample of 10 million U.S. Internet users.

To me, these numbers suggest that Bing's granular strategy, in which it focuses on the verticals and leaves a lot of the traditional keyword search to Google, could be paying off. True, it only occupies some 2.84 percent market share for the Automobile vertical, 3.74 percent for Health, 2.51 for Shopping and 3.11 for Travel; but its year-over-year increases suggest that users could be relying on Bing more for specific subject searches.

Back in March, my colleague Clint Boulton interviewed Bing Director Stefan Weitz, who told him that Microsoft is primarily interested in claiming market share in nontraditional areas such as event-driven tasks and commercial queries. Describing search as "not a zero-sum game," Weitz added: "As we look at how people are using the Web itself and how the Web is changing, we think we can expand that which people do with these engines. We can grow the overall pie, the overall number of searches that are happening across the Web."

Microsoft continues to try and improve Bing with a variety of features, including one-click access to more in-depth information (such as images, news, videos and reference articles) about particular search terms. But its main competitive differentiator is the tabs on its main search page that allow users to kick off their search into subcategories such as Shopping and Travel. Bing might not be anywhere close to toppling Google, but again, the Hitwise numbers suggest that its policy of forsaking the generalized keyword-search battle for a more granular approach could be paying off.

What do you think? Is Microsoft applying the right strategy in search?