The researcher found that Bing's rise that month, to 15.1%, was due mostly to a 0.6% drop in Yahoo's market share. The rankings come after Bing tied Yahoo in November.
Nevertheless, it's cause for celebration among the team behind the three-year-old search engine at Microsoft, which powers Yahoo search. Last year at this time, Bing's share was 12% vs. 16% for Yahoo. Bing's growth is a reflection of Microsoft's characteristic patience -- the search engine has been a drag on earnings.
However, the numbers also evince Yahoo's continuing decline. Once the number one search engine, Yahoo lost that ranking to Google in 2000. Over time, Google, which became Yahoo's default search provider that year, became as well known as Yahoo. The two parted ways in 2004. Since that time, Yahoo has seen an erosion in market share in search and has failed in its bid to reverse its fortunes despite a steady stream of would-be turnaround CEOs. (PayPal's Scott Thompson became the latest to fill that slot earlier this month.)